Crispy Onion Chicken Sandwich

Featured in: Oven & Pan Creations

This mouthwatering sandwich combines juicy buttermilk-marinated fried chicken, golden crispy onions, and creamy garlic aioli on soft brioche. The chicken thighs are seasoned with garlic and paprika, then dredged in a flavorful breading and fried until golden brown. Thinly sliced onions are coated and fried separately for maximum crunch. The homemade aioli brings everything together with lemon and Dijon mustard notes. Perfect for lunch or dinner, this American favorite takes just 50 minutes from start to finish and serves four hungry appetites.

Updated on Sun, 18 Jan 2026 11:14:00 GMT
Golden-brown Crispy Onion Chicken Sandwich with juicy buttermilk-fried chicken thighs piled high on a soft brioche bun, topped with crunchy fried onions.  Pin It
Golden-brown Crispy Onion Chicken Sandwich with juicy buttermilk-fried chicken thighs piled high on a soft brioche bun, topped with crunchy fried onions. | casaflavors.com

The smell of frying onions used to drive my neighbors crazy every Sunday afternoon. I'd crack open the kitchen window just enough to let the steam out, and within minutes someone would text asking what I was making. This sandwich started as a way to use up leftover buttermilk, but it turned into the thing people actually requested by name. The first batch of crispy onions burned because I wasn't paying attention, but even those tasted so good I kept eating them straight from the paper towel.

I made these for a birthday dinner once, and my friend who claimed she didn't like fried chicken ate two. She kept saying it was the onions that got her, but I saw her pulling apart the chicken to check how juicy it was. We ended up sitting on the porch with a pile of sandwiches and a bowl of pickles, talking until the sun went down. That night taught me that sometimes the best meals are the ones you can hold in your hands.

Ingredients

  • Boneless, skinless chicken thighs: Thighs stay tender and juicy even if you overcook them slightly, which makes them way more forgiving than breasts.
  • Buttermilk: This is what makes the chicken so soft and flavorful, and it helps the breading stick without any fuss.
  • Garlic powder and paprika: These go into the marinade to build flavor from the inside out, not just on the surface.
  • All-purpose flour and cornstarch: The cornstarch makes the crust extra crispy and light, not dense or greasy.
  • Smoked paprika: Adds a subtle smokiness to the breading that makes people ask what your secret is.
  • Yellow onion: Slice it thin so it fries up fast and shatters when you bite into it.
  • Mayonnaise: The base for a quick aioli that pulls everything together with just a few ingredients.
  • Garlic clove and lemon juice: These brighten up the mayo and give it enough punch to stand up to the fried chicken.
  • Dijon mustard: Just a little bit adds tang and keeps the aioli from tasting flat.
  • Brioche buns: Soft enough to soak up some of the aioli but sturdy enough not to fall apart in your hands.
  • Vegetable oil: Use something neutral with a high smoke point so you can fry without any burnt taste.

Instructions

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Marinate the chicken:
Whisk buttermilk with garlic powder, paprika, salt, and pepper until everything is blended, then add the chicken thighs and make sure they're completely covered. Let them sit in the fridge for at least thirty minutes, though a few hours makes them even better.
Prepare the breading:
Mix flour, cornstarch, smoked paprika, salt, and pepper in a shallow dish. This is your coating station, so keep it close to the stove.
Coat the onions:
Toss the sliced onions with flour, salt, and pepper until every piece has a light dusting. Shake off any excess so they fry up crispy instead of clumpy.
Fry the onions:
Heat about an inch of oil to 350°F in a large skillet, then fry the onions in small batches for two to three minutes until they turn golden and crispy. Move them to paper towels to drain right away.
Bread the chicken:
Pull each thigh out of the buttermilk and let the extra drip off, then press it into the breading mixture on both sides. Make sure it's well coated so you get that satisfying crunch.
Fry the chicken:
Slide the breaded thighs into the hot oil and cook for five to seven minutes per side until the crust is deep golden and the chicken is cooked through. Let them rest on a wire rack or paper towels so they stay crispy.
Make the aioli:
Stir together mayonnaise, minced garlic, lemon juice, Dijon, salt, and pepper in a small bowl. Taste it and adjust the seasoning until it feels balanced.
Toast the buns:
If you want, butter the cut sides of the brioche buns and toast them in a skillet until they're golden. It's optional, but it adds a nice texture.
Assemble the sandwiches:
Spread aioli on both sides of each bun, layer with lettuce if you're using it, add a piece of fried chicken, pile on the crispy onions, and close it up. Serve them right away while everything is still warm.
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Close-up of a Crispy Onion Chicken Sandwich stacked with golden onions and creamy aioli, served alongside crispy french fries on a rustic table.  Pin It
Close-up of a Crispy Onion Chicken Sandwich stacked with golden onions and creamy aioli, served alongside crispy french fries on a rustic table. | casaflavors.com

One evening I packed these sandwiches in foil and brought them to a friend's backyard hangout. Everyone was skeptical about eating something that had been wrapped up, but the buns had soaked up just enough of the aioli and the chicken was still warm. We ended up sitting around the fire pit, passing around hot sauce and laughing about how good cold beer tastes with fried chicken. It's one of those meals that makes people relax and talk more, and I think that's worth as much as the recipe itself.

How to Get the Crispiest Chicken

The trick is to let the breaded chicken sit for a few minutes before it hits the oil. This lets the coating stick to the surface and creates a better crust. If you fry it right away, sometimes the breading slides off in patches. I also learned that pressing the flour mixture into the chicken, instead of just dipping it, makes a huge difference in how much coating actually stays on.

What to Do with Leftover Crispy Onions

I always make extra onions because they're good on almost everything. Toss them on top of a salad, stir them into scrambled eggs, or just eat them as a snack with a little hot sauce. They keep for a day or two in an airtight container, though they're never quite as crispy as when they're fresh. If they soften up, you can reheat them in the oven at 350°F for a few minutes to bring some of the crunch back.

Serving Suggestions and Simple Sides

This sandwich is rich and filling, so I usually serve it with something bright and crunchy on the side. A simple slaw with vinegar and a little sugar works really well, or even just some dill pickles straight from the jar. Sweet potato fries are great if you want something more substantial, and they don't compete with the flavors of the sandwich.

  • Add a few dashes of hot sauce to the aioli if you like a little heat without overwhelming the other flavors.
  • If you don't have brioche buns, a soft potato roll or even a ciabatta roll works just fine.
  • You can swap chicken breasts for thighs, but keep an eye on the cooking time since breasts dry out faster.
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Homemade Crispy Onion Chicken Sandwich with toasted brioche, lettuce, and crispy fried onions, perfect for a classic American lunch. Pin It
Homemade Crispy Onion Chicken Sandwich with toasted brioche, lettuce, and crispy fried onions, perfect for a classic American lunch. | casaflavors.com

This sandwich has become my go-to when I want to make something that feels special but doesn't require a ton of complicated steps. Every time I make it, I remember why sometimes the best food is the kind you can eat with your hands and share with people you actually like being around.

Recipe FAQs

Can I prepare the chicken ahead of time?

Yes, marinate the chicken thighs in buttermilk for up to 4 hours in advance. For best texture, fry the chicken and crispy onions just before serving to maintain crunchiness.

What oil temperature is best for frying?

Heat oil to 350°F (175°C) for optimal results. This temperature ensures the coating becomes golden and crispy while the chicken cooks through without burning. Use a thermometer to maintain consistent heat.

How do I keep the onions crispy?

Drain fried onions immediately on paper towels to remove excess oil. Store them separately from the assembled sandwich until just before serving. This prevents them from absorbing moisture and losing their crunch.

Can I use chicken breasts instead of thighs?

Absolutely. Chicken breasts work well and will reduce cooking time slightly. Pound them to even thickness so they cook uniformly and stay juicy throughout the frying process.

What can I serve alongside this sandwich?

Pickles, coleslaw, and french fries pair perfectly. A crisp salad or pickled vegetables add brightness and balance the richness of the fried components beautifully.

How do I make the aioli spicier?

Add hot sauce, cayenne pepper, or sriracha to the aioli base. Alternatively, incorporate a pinch of cayenne into the breading mixture for heat that builds throughout each bite.

Crispy Onion Chicken Sandwich

Buttermilk-marinated fried chicken with crunchy onions and garlic aioli on brioche—a satisfying American classic.

Prep Time
25 mins
Time to Cook
25 mins
Overall Time
50 mins
Created by Fiona Chambers


Skill Level Medium

Cuisine Type American

Makes 4 Portions

Dietary Details None specified

What You'll Need

Chicken & Marinade

01 4 boneless, skinless chicken thighs
02 1 cup buttermilk
03 1 teaspoon garlic powder
04 1 teaspoon paprika
05 1/2 teaspoon salt
06 1/2 teaspoon black pepper

Breading

01 1 cup all-purpose flour
02 1/2 cup cornstarch
03 1 teaspoon smoked paprika
04 1 teaspoon salt
05 1/2 teaspoon ground black pepper

Crispy Onions

01 1 large yellow onion, thinly sliced
02 1/2 cup all-purpose flour
03 1/2 teaspoon salt
04 1/2 teaspoon black pepper
05 Vegetable oil for frying

Aioli

01 1/2 cup mayonnaise
02 1 large garlic clove, minced
03 1 tablespoon fresh lemon juice
04 1/2 teaspoon Dijon mustard
05 Salt and pepper to taste

Assembly

01 4 brioche buns, sliced
02 Butter for toasting buns, optional
03 Lettuce leaves, optional

How to Make It

Step 01

Prepare Buttermilk Marinade: In a mixing bowl, whisk together buttermilk, garlic powder, paprika, salt, and black pepper. Submerge chicken thighs in marinade, ensuring complete coverage. Cover bowl and refrigerate for minimum 30 minutes or up to 4 hours.

Step 02

Mix Breading Mixture: In a shallow dish, combine flour, cornstarch, smoked paprika, salt, and black pepper. Set aside for chicken coating.

Step 03

Coat Onion Slices: In a separate bowl, toss sliced onions with flour, salt, and black pepper until evenly coated on all sides.

Step 04

Fry Crispy Onions: Heat 1 inch of vegetable oil in a large skillet to 350°F. Working in batches, fry coated onions for 2-3 minutes per batch until golden and crisp. Transfer to paper towels to drain excess oil.

Step 05

Bread Chicken Thighs: Remove chicken from marinade, allowing excess buttermilk to drip off. Dredge each thigh in breading mixture, pressing firmly to ensure coating adheres properly.

Step 06

Fry Chicken: Fry breaded chicken in the same hot oil for 5-7 minutes per side until internal temperature reaches 165°F and exterior is golden brown. Transfer to wire rack or paper towels to drain.

Step 07

Prepare Aioli: In a small bowl, whisk together mayonnaise, minced garlic, lemon juice, Dijon mustard, salt, and pepper until smooth and well combined.

Step 08

Toast Brioche Buns: Optionally, butter brioche buns and toast in skillet over medium heat until golden brown on cut sides, approximately 1-2 minutes per side.

Step 09

Assemble Sandwiches: Spread aioli on both cut surfaces of each bun. Layer with lettuce if desired, followed by fried chicken thigh, generous amount of crispy onions, and top bun. Serve immediately.

Equipment Needed

  • Mixing bowls
  • Large skillet or deep fryer
  • Tongs
  • Wire rack or paper towels
  • Knife and cutting board
  • Thermometer for oil temperature verification
  • Shallow dishes for breading

Allergy Info

Be sure to look over every ingredient for allergens, and talk to a health expert with any concerns.
  • Contains eggs in mayonnaise component
  • Contains wheat in flour and brioche buns
  • Contains milk in buttermilk and butter
  • Contains mustard in aioli component
  • Brioche buns may contain soy or additional allergens; verify packaging

Nutrition per Serving

Nutritional info is for general reference and isn't medical guidance.
  • Caloric Value: 670
  • Fats: 32 g
  • Carbohydrates: 61 g
  • Proteins: 32 g