I finally nailed French Fried Onions that come out perfectly crisp with bold onion flavor and an optional Cajun kick, the homemade topping your green bean casserole has been waiting for.

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I love messing with classics, so my Copycat French’s Crispy Onions started as a late night experiment after I wanted more crunch. Big sweet punch from large yellow onions, very thinly sliced and a little tang from buttermilk make them sing, and if you nudge the heat they get a tongue tingling kick.

They somehow elevate a plain side into something loud and celebratory, not just holiday background noise. I wanted the familiar store vibe but with a home made edge, flaws and all.

If you like French Fried Onions you might get hooked, dont say I didnt warn you.

Ingredients

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Onions bring fiber, mild sweetness and natural umami when fried, crisping up nicely.
Buttermilk adds tang, tenderizes onions, contributes protein and slight lactic sourness.
Egg binds batter, adds eggy richness and protein, helps coating adhere.
All purpose flour gives structure, carbohydrates for browning and a hearty crust.
Cornstarch lightens batter, boosts crispness, reduces chewiness without flavor.
Neutral oil fries at high heat, adds calories, not very heart healthy.
Salt pepper garlic give savory depth, cayenne gives heat and bright spice.

Ingredient Quantities

2 large yellow onions, very thinly sliced

1 cup buttermilk (or 3/4 cup milk + 1 tbsp vinegar)

1 large egg

1 1/4 cups all purpose flour

1/2 cup cornstarch

1 tsp kosher salt

1/2 tsp freshly ground black pepper

1/2 tsp garlic powder

1/4 to 1/2 tsp cayenne or Cajun seasoning, optional

2 to 3 cups neutral oil like vegetable or canola, for frying

How to Make this

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1. Thinly slice 2 large yellow onions (use a mandoline if you got one) and separate into rings; you want very thin slices so they crisp up fast.

2. Whisk together 1 cup buttermilk (or 3/4 cup milk + 1 tbsp vinegar) and 1 large egg in a bowl, then soak the sliced onions in that for 15 to 30 minutes so they get slightly tender and the wet mix will help the coating stick.

3. In a large shallow bowl combine 1 1/4 cups all purpose flour, 1/2 cup cornstarch, 1 tsp kosher salt, 1/2 tsp freshly ground black pepper, 1/2 tsp garlic powder and 1/4 to 1/2 tsp cayenne or Cajun seasoning if you want the kick.

4. Pour 2 to 3 cups neutral oil like vegetable or canola into a heavy pot to a depth of about 2 to 3 inches and heat to 350°F. If you don’t have a thermometer drop a small piece of coated onion in; it should sizzle and float up quickly.

5. Working in small batches, lift onions from the buttermilk, shake off excess (dont try to dry them totally) then dredge in the flour mixture pressing the flour into the onions so it clings. For extra crunch you can quickly dip back into the buttermilk and coat again in the flour mix.

6. Fry the onions in batches so the oil temperature stays around 350 to 375°F. Stir gently with a slotted spoon so pieces separate, and fry until deep golden and crispy, about 2 to 3 minutes per batch depending on thickness.

7. Remove with a slotted spoon onto a wire rack set over paper towels to drain, and immediately sprinkle a little extra kosher salt to taste while they’re hot.

8. Let the onions cool completely on the rack so they get extra crispy, don’t pile them up while warm or they’ll steam and go soggy.

9. Use right away on your green bean casserole or store in an airtight container at room temp for up to 2 days; to re-crisp, bake on a sheet at 350°F for 4 to 6 minutes.

Equipment Needed

1. Large heavy pot or Dutch oven for frying (2 to 3 in oil)
2. Candy/fry thermometer to hold 350 to 375°F
3. Mandoline or sharp chef knife and a cutting board for super thin onion slices
4. Large shallow bowl for the flour + cornstarch mix
5. Medium bowl for the buttermilk + egg and a whisk
6. Slotted spoon or spider/skimmer for stirring and lifting fried onions
7. Tongs for moving onion rings between bowls and oil
8. Wire rack set over a rimmed baking sheet plus paper towels for draining
9. Measuring cups and spoons for the flour, cornstarch and seasonings

FAQ

Q: How thin should I slice the onions?

Really thin, about paper thin or 1 to 2 mm. A mandoline makes this easy, but a sharp knife works if you go slow. Thinner = crispier, thicker = soggier.

Q: What oil and temperature should I use for frying?

Use a neutral oil like vegetable or canola. Heat to about 350 to 365°F. Fry in small batches so the temp doesn’t drop, and don’t crowd the pan or they’ll steam instead of crisp.

Q: Any tips to keep them extra crispy and not greasy?

Drain on a rack over paper towels right after frying, then blot gently. If you need them to stay crisp for a while, hold them in a single layer on a baking sheet in a 200°F oven for 10 to 15 minutes.

Q: Can I bake them instead of frying?

Yes but they wont be exactly the same. Toss sliced onions in the batter, spread on a wire rack over a sheet and bake at 425°F, flipping once. They’ll be lighter and less greasy but not as deeply golden as fried ones.

Q: How long do they store and how do I re-crisp them?

Store in an airtight container at room temp up to 3 days. To re-crisp, spread on a baking sheet and warm at 300°F for 5 to 10 minutes until crunchy again. Don’t refrigerate or they get soggy.

Q: Can I change the seasoning or omit the egg/buttermilk?

You can tweak spices, add more garlic powder, or use cayenne for heat. Egg and buttermilk help the coating stick and brown, but you can try a milk+vinegar substitute listed in the ingredients if you dont have real buttermilk.

Copycat French’s Crispy Onions Recipe Substitutions and Variations

Buttermilk (swap for plain Greek yogurt thinned with milk or water — about 3/4 cup yogurt + 1/4 cup water, or use 3/4 cup milk + 1 tbsp lemon or vinegar, or for dairy free use unsweetened soy or oat milk + 1 tbsp vinegar). Keeps the tang and helps the coating stick, just make sure yogurt is smooth so it coats evenly.
Egg (swap for a flax “egg” 1 tbsp ground flaxseed + 3 tbsp water let sit 5 min, or 1 tbsp chia + 3 tbsp water, or 3 tbsp aquafaba for a vegan binder). Flax and chia bind well but they wont brown exactly like real egg.
All purpose flour (swap for white rice flour for extra crisp, or a gluten free 1:1 baking blend; chickpea flour gives a nuttier flavor). Rice flour gives the crispiest results, chickpea is heavier but tasty.
Cornstarch (swap for potato starch, tapioca starch, or arrowroot powder). Potato starch usually yields the best crisp, tapioca adds a touch of chew.

Pro Tips

1) Slice the onions paper thin and separate the rings with your fingers before coating, otherwise they’ll stick together and you end up with clumps. Dont force them dry after the soak, a little moisture helps the flour cling.

2) For extra crunch double-dredge: press the flour into the rings, dunk briefly back in the buttermilk, then flour again. Works way better than just one coat.

3) Keep the oil steady at about 350 to 375 F and fry in small batches so the temp doesn’t crash. Test with a tiny scrap first, and dont overcrowd the pot or the pieces will steam not crisp.

4) Drain on a wire rack, salt immediately while hot because the salt sticks better, then let cool completely in a single layer so they stay crisp. To bring leftovers back to life, bake on a sheet in a 350 F oven for a few minutes until crunchy again.