In a bowl, combine buttermilk, salt, black pepper, garlic powder, onion powder, and paprika. Add the chicken breasts, ensuring they are fully submerged. Cover and refrigerate for at least 2 hours, preferably overnight.

Prepare the Breading

In a shallow dish, whisk together flour and cornstarch. Season with a pinch of salt and pepper.

Fry the Chicken

Heat vegetable oil in a deep skillet over medium-high heat. Remove chicken from the brine and let excess liquid drip off. Dredge each piece in the flour mixture, shaking off excess. Carefully place chicken in the hot oil and fry for 5-7 minutes per side, or until golden brown and cooked through. Use a thermometer to ensure the internal temperature reaches 165°F (74°C).

Prepare the Pickles

While the chicken is frying, prepare the pickles. You can use store-bought pickles or make your own if desired.

Assemble the Sandwich

Spread mayo on the bottom half of each brioche bun. Place a fried chicken breast on top, add pickles, and then top with the other half of the bun.

Serve

Serve immediately while hot with your favorite side dishes.