Crispy Sourdough Onion Rings with Homemade Ranch Dip

Last updated on April 15th, 2025 at 09:44 pm

These sourdough onion rings are ultra crispy, golden, and bursting with flavour — the perfect way to put your sourdough discard to work. Lightly battered and fried to golden perfection, they’re served with a cool, creamy ranch dip that’s made for serious dipping — flavour-packed and delicious. Whether you’re making them for game day, as a casual appetizer, or a crowd-pleasing side, this recipe is simple to make, totally satisfying and requires no fancy tools — just your sourdough discard, a few pantry staples, and a good pot for frying.

Why You’ll Love These Sourdough Onion Rings

These aren’t your average onion rings. They’re light, crispy, packed with flavour, and a brilliant way to use up that jar of sourdough discard sitting in your fridge. Whether you’re cooking for a crowd or just craving something salty and satisfying, these rings are the kind of snack that disappears fast.

A Clever Way to Use Sourdough Discard

If you bake sourdough, you know the discard dilemma — tossing it feels wasteful, but it builds up fast. These sourdough onion rings turn that extra discard into gold. The acidity in the discard adds a subtle tang and complexity to the batter, enhancing the flavour without overpowering the sourdough onion rings. It’s a no-waste solution that tastes amazing.

Super Crispy, Never Greasy

The batter here is inspired by techniques I learned working in Michelin-starred kitchens — we always looked for ways to add a crisp element to the plate, not just for flavour but for contrast. Texture is everything. This batter uses cornstarch, a touch of flour, and sparkling water to stay light and airy, so the rings fry up shatteringly crisp without soaking in oil.

Made with Simple Pantry Ingredients

You don’t need a deep fryer or hard-to-find ingredients. Sourdough discard, onion, flour, cornstarch, sparkling water — it’s all stuff you probably already have on hand. The oil is key, but even a small batch in a cast iron pan works beautifully.

Perfect with Homemade Ranch

We skip the store-bought dips and pair these rings with a cool, creamy homemade ranch dressing. It’s fresh, tangy, and balances the richness of the onion rings perfectly. Once you try this from-scratch version, you might never go back to bottled.

What You’ll Need

Before you get started, it’s a good idea to gather everything you’ll need. This recipe doesn’t require a deep fryer or any fancy tools — just a few kitchen staples and a bit of prep.

Equipment

• Cutting board – for prepping onions and garlic
• Chef’s knife – or a sharp serrated knife for clean onion cuts
• Mixing bowls – one for the batter, one for dredging
• Digital kitchen thermometer – for accurate oil temp (aim for 380°F / 193°C)
• Heavy Dutch oven saucepan or cast iron skillet – retains heat well for consistent frying
• Slotted spoon or spider – for safely removing onion rings from hot oil
• Plate lined with paper towel – to drain excess oil
• Microplane or fine grater – for garlic in the ranch dip
• Whisk – for both batter and ranch
• Tweezers or small tongs – for placing rings gently in oil

For the Sourdough Onion Ring Batter

For the Homemade Ranch Dip

For Frying & Serving

*Recommended oils: grapeseed, vegetable, or canola — all have high smoke points and a neutral flavour that won’t overpower the batter.

How to Cut Onion Rings

Cutting the onions properly is the first step toward achieving perfectly crispy, evenly cooked sourdough onion rings. It might seem simple, but the way you slice — and what you do with the rings after — can make all the difference in both texture and flavour.

Slice Thickness Matters

Start by trimming the root and stem ends of your onions and peeling off the papery skin. Place the onion flat-side down on your cutting board and slice it crosswise into 1.25 cm (½ inch) thick rounds.

This thickness is ideal: thin enough to cook through quickly, but thick enough to hold up to the batter and frying process without collapsing.

After slicing, separate the rings gently with your fingers, starting from the centre and working your way out. You can group the larger and smaller rings separately if you’d like — this makes it easier to manage cooking times later on.

Pro Tip: Use a sharp chef’s knife or a serrated knife for cleaner cuts. Dull blades can crush the onion, making the rings harder to separate and more likely to break apart when battering.

How to Make the Sourdough Onion Ring Batter

This batter is the key to that ultra-crispy, shatteringly light crust. It’s simple, but the combination of sourdough discard and sparkling water gives it a distinct flavour and delicate texture that really sets these onion rings apart.

Why Use Sourdough Discard?

Sourdough discard adds a subtle tang and complexity to the batter without being overpowering. It also reacts beautifully with cold sparkling water to create those airy bubbles that make the crust so crisp.

If you bake sourdough often, you know how discard piles up fast — this is one of the most satisfying ways to put it to use. And don’t worry if it’s been in the fridge a few days — it doesn’t need to be bubbly or active.

To make the batter:

1. In a mixing bowl, combine the cold sparkling water and sourdough discard. Whisk together until smooth and fully blended.
2. In a separate bowl, whisk together the cornstarch, flour, and a pinch of fine sea salt.
3. Add the dry ingredients to the wet mixture, and whisk gently until the batter is smooth. It should have the consistency of a thin pancake batter — just thick enough to coat the back of a spoon and cling to the onion rings without dripping off too quickly.

Pro Tip: Use the coldest sparkling water you can — the carbonation and temperature both help create a crisp, airy crust.

Let the Batter Rest

Once your batter is mixed, let it rest at room temperature for 20 minutes before using. This allows the flour and starch to fully hydrate and improves the coating’s texture and adhesion to the sourdough onion rings.

It’s a small step, but it makes a big difference — especially if you’re aiming for onion rings that stay crispy even after a few minutes out of the oil.

Frying onion rings at home might sound intimidating, but it’s easier than you think — especially if you set yourself up properly. The key to success is choosing the right oil, managing the temperature, and working in batches.

1. Choosing the Right Oil

Look for a neutral, high-smoke-point oil that won’t overpower the flavour of the batter. Grapeseed, canola, or vegetable oil are all excellent choices for deep or shallow frying.

You’ll need around 1 litre (4 cups) of oil, depending on the size of your pan. There should be enough depth to submerge the onion rings at least halfway if shallow frying.

2. Frying Temperature Tip

Heat your oil to 365–395°F (185–200°C) in a heavy-bottomed pan like a cast iron skillet or Dutch oven. This range allows the batter to crisp up quickly without absorbing too much oil.

Use a digital thermometer to keep things consistent. If you don’t have one, drop in a small bit of batter — if it sizzles and rises to the surface, you’re good to go.

Pro Tip: The more onion rings you add at once, the more the oil temperature will drop. Work in batches to maintain even heat.

3. Shallow Fry vs. Deep Fry

• Deep Frying: Best for even colour and crispness. Less flipping, more control.
• Shallow Frying: Easier to set up, but needs more attention. Flip each ring halfway through and watch the temp closely.
• Use a heavy pan with good heat retention — cast iron is ideal.

4. Step-by-Step: How to Fry the Onion Rings

1. Heat oil to 365–395°F (185–200°C).
2. Dip each onion ring into the batter, allowing the excess to drip off.
3. Carefully place the rings into the hot oil, working in batches to avoid crowding.
4. Fry for 3–4 minutes per side or until golden brown and crisp.
5. Remove using a slotted spoon or spider, and transfer to a paper towel-lined plate.
6. Season with salt while still hot to lock in the flavour.

Pro Tip: The batter should be light and crisp, clinging to the onion without being doughy.

• If the rings darken too fast, reduce the heat.
• If they come out pale or greasy, your oil’s too cool.

Make the Homemade Ranch Dip

No need to reach for the bottle — this homemade ranch is fresh, creamy, and easy to make in just a few minutes. It balances the crispy richness of the sourdough onion rings with a cool, tangy flavour that keeps you going back for more.

1. Add everything to a mixing bowl and whisk until smooth and well combined. The buttermilk loosens the yogurt, creating a pourable, dippable consistency that coats beautifully.
2. Cover and chill for 15–30 minutes to let the flavours come together. It keeps in the fridge for up to 5 days.

Pro Tip: For an ultra-smooth ranch, you can blend everything in a mini food processor or use an immersion blender — but a regular whisk works just fine.

Ranch Variations You Can Try

Want to switch it up? Here are a few simple ways to adapt your ranch based on what you have on hand (or what you’re craving):

• Creamier Ranch: Sub half the Greek yogurt with mayo for a richer base
• Spicy Ranch: Add a few dashes of hot sauce or a pinch of cayenne
• Lemon & Herb Ranch: Increase the lemon juice and add parsley or tarragon
• Garlic Lover’s Ranch: Use freshly grated garlic instead of powder for a sharper kick
• Smoky Ranch: Add a touch of smoked paprika or chipotle powder

Serving Suggestions & Variations

These sourdough onion rings are best served hot and fresh — straight from the fryer, while the coating is still crisp and golden. They’re incredibly versatile and work in all kinds of settings, from casual snacks to elevated appetizers.

Here’s how we love to serve them:

• With ranch dip on the side — cool, tangy, and the perfect contrast to the hot, crispy rings. Serve it in a small bowl for dipping or drizzle it directly over the rings on the plate.
• On a platter for sharing — pile them high and sprinkle with a pinch of flaky sea salt or fresh herbs like chives or parsley just before serving.
• As a side dish — serve alongside grilled meats, burgers, or sandwiches for an elevated, homemade twist on pub-style comfort food.
• Topped with extras — try finishing them with a squeeze of fresh lemon juice, a dusting of smoked paprika, or a touch of honey for a sweet-savoury twist.

No matter how you serve them, these onion rings are the kind of thing that disappear fast — so make more than you think you’ll need.

These sourdough onion rings are at their absolute best served immediately — hot from the oil, crispy on the outside, and tender inside. That’s when the batter is at its lightest and most satisfying.

If you’re serving them for guests or during a meal, try to time your frying as close to serving as possible. You can keep them warm in a low oven (around 90°C / 195°F) for a short time while you finish frying the batch.

Frequently Asked Questions (FAQs)

Can I make the ranch dip ahead of time?

Yes! The ranch actually tastes even better after it sits for a bit. Make it up to 3 days in advance and store it in an airtight container in the fridge. Just give it a stir before serving.

Can I bake these instead of frying?

Technically yes, but baking won’t give you the same crispy, airy texture. The batter is designed for frying, so it won’t set the same way in the oven.

If you’re looking for a lower-oil option, the air fryer is a better alternative. You’ll still get some crispness, though the texture will be a little different.

Can I use bubbly starter instead of discard?

Yes — if your starter is active and bubbly, it will still work. The flavour will be slightly milder and a bit fresher than discard, but the result is still delicious. Just keep in mind that a bubbly starter may create a slightly thicker batter — you can thin it with an extra splash of sparkling water if needed.

How long does the batter last?

The batter is best used within 1–2 hours after mixing. You can make it a bit ahead and keep it in the fridge, but it may lose some of its lightness as the carbonation fades. Be sure to give it a good stir before using it, and don’t skip the resting time if you’ve just made it.

More Sourdough Discard Recipes

If you love these Sourdough Onion Rings and have extra sourdough discard them in the fridge. Don’t let it go to waste — here are a few more recipes that make the most of it:

• Sourdough Discard Waffles – Light and crisp with a tangy edge, perfect for weekend brunch.
• Sourdough Cornbread with Buttermilk – Moist, flavourful, and the perfect side for everything from chilli to BBQ.
• Sourdough Discard Crackers – Thin, crunchy, and endlessly snackable with just the right amount of tang.
• Sourdough English Muffins – A classic, chewy breakfast favourite made even better with discard.

Want more ideas? Browse all sourdough discard recipes here

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Sourdough Onion Rings Recipe Card:

Sourdough Discard Onion Rings

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• Author: Matthew James Duffy
• Total Time: 40 minutes
• Yield: 2 servings 1x

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Description

These sourdough onion rings are ultra crispy, golden, and full of flavour. Made with sourdough discard and served with a cool, creamy homemade ranch dip, they’re the perfect appetizer, snack, or game-day treat. No fancy tools required — just pantry staples and a good pan for frying.

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Ingredients

Scale 1x2x3x

For the Sourdough Onion Ring Batter:

• 50 g cornstarch (~¾ cup)

• 25 g all-purpose flour (~⅓ cup)

• 40–50 g sourdough discard (~¼ cup)

• 1 pinch fine sea salt (~⅛ tsp)

• 100 g cold sparkling water (100 ml)

For the Homemade Ranch Dip:

• 250 g Greek yogurt (1 cup)

• 75 g buttermilk (¼ cup)

• 5–10 g chives, finely chopped (2 tbsp)

• 5–10 g dill, finely chopped (2 tbsp)

• 5 g lemon juice (1 tbsp)

• 2 g onion powder (¾ tsp)

• 2 g garlic powder (¾ tsp)

• 2 g sea salt (¾ tsp)

• 1 g cracked black pepper (½ tsp)

For Frying & Serving:

• ~1 L high-heat neutral oil (4 cups, adjust as needed) — grapeseed, canola, or vegetable

• 2 medium sweet onions (Vidalia or Spanish), sliced into 1.25 cm (½ inch) rings

• Sea salt, for seasoning

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Instructions

1. Prepare the Onions:
   Slice onions crosswise into ½-inch rings. Separate into individual rings and set aside.

2. Make the Batter:
   In a medium bowl, whisk together the cold sparkling water and sourdough discard until smooth. In a separate bowl, mix the cornstarch, flour, and salt. Add the dry ingredients to the wet mixture and whisk until the batter is smooth and has the consistency of a thin pancake batter.

3. Let the batter sit at room temperature for 20 minutes to hydrate.

4. Heat the Oil:
   Heat oil in a Dutch oven or heavy skillet to 365–395°F (185–200°C). Use a thermometer for accuracy.

5. Fry the Onion Rings:
   Dip onion rings into the batter, letting excess drip off. Carefully place into the hot oil, working in batches. Fry for 3–4 minutes per side, until golden and crisp. Remove and drain on a paper towel–lined plate. Season with salt while hot.

6. Make the Ranch Dip:
   In a bowl, whisk together all ranch ingredients until smooth. Chill for 15–30 minutes before serving.

7. Serve:
   Serve the sourdough onion rings immediately with ranch on the side or drizzled over top.

Notes

Resting the batter for 20 minutes is key to getting that light, crisp coating that sticks beautifully to the onion rings.

Use the coldest sparkling water you can — the carbonation and chill both help keep the batter airy.

For best results, fry in batches and keep the cooked rings warm in a low oven (around 90°C / 195°F) while you finish the rest.

The batter is best used within 1 to 2 hours of mixing, as it will lose some of its lightness over time.

• Prep Time: 20 minutes
• Cook Time: 20 minutes
• Category: Sourdough Discard
• Method: Deep Frying
• Cuisine: American