If using breasts, cut each into two thinner cutlets (about 4 pieces total). Pat the chicken dry with paper towels. Place chicken in a shallow dish and pour buttermilk and 2 tbs hot sauce over it. Cover and refrigerate for at least 30 minutes (up to 4 hours) to tenderize and add flavor.

Make dredge

In a shallow bowl or pie plate, whisk together flour, cornstarch, garlic powder, onion powder, smoked paprika, salt, and black pepper until evenly combined.

Dredge chicken

Remove chicken from buttermilk, allowing excess to drip off. Press each piece firmly into the flour mixture, coating completely. For extra crispiness, dip back briefly into the buttermilk and press into the flour mix again for a double coat.

Fry chicken

Pour vegetable oil into a large skillet to a depth of about 1/2 inch (about 1 cup). Heat over medium-high until oil reaches 350°F (175°C) or a small piece of bread sizzles and browns in ~30 seconds. Fry chicken pieces 3–4 minutes per side until golden brown and internal temperature reaches 165°F (74°C). Work in batches to avoid crowding. Transfer fried chicken to a wire rack set over a baking sheet to drain and keep warm.

Toss in Buffalo sauce

Place the warm fried chicken in a bowl. Pour 1/2 cup Buffalo sauce over the chicken and toss gently to coat each piece evenly. Set aside.

Buffalo Blanc Sauce

In a small bowl whisk together mayonnaise, sour cream, Greek yogurt, lemon juice, apple cider vinegar, minced garlic, and hot sauce (if using). Season with salt and pepper. Taste and adjust acidity or heat as desired. Chill until ready to assemble (at least 10 minutes).

Blue Cheese Dressing

In a bowl combine blue cheese crumbles, mayonnaise, sour cream, and milk. Stir until you reach desired consistency. Add lemon juice, salt, and pepper. Lightly mash some of the blue cheese with the back of a spoon to distribute flavor while leaving some chunky pieces. Refrigerate until assembly.

Sandwich Assembly

Prep vegetables and buns

Slice tomato into 4 rounds and sprinkle lightly with 1/4 tsp salt. Separate and rinse lettuce leaves and dry. Butter the cut sides of the brioche buns. Heat a skillet over medium heat and toast buns butter-side down until golden, about 1–2 minutes.

Assemble sandwiches

Spread about 1 tablespoon Buffalo Blanc Sauce on the bottom half of each toasted bun. Place one piece of buffalo-coated crispy chicken on each bun bottom. Add 2 tbs blue cheese dressing over the chicken (or more to taste). Top with a lettuce leaf, 1 tomato slice, a few rings of red onion, and 2 pickle slices. Finish with a drizzle of any remaining Buffalo Blanc Sauce on the bun top, then cap the sandwich and press gently.

Serve

Serve immediately while chicken is hot and crispy. Provide extra blue cheese dressing and Buffalo Blanc Sauce on the side for dipping. Leftover components (sauces) keep refrigerated for up to 3 days.