Combine the buttermilk, hot sauce, and a pinch of salt in a bowl. Add the chicken thighs, submerge them fully, and marinate for at least 20 minutes at room temperature or up to 4 hours in the fridge.

Whisk the flour, cornstarch, garlic powder, onion powder, smoked paprika, salt, black pepper, and cayenne together in a shallow bowl. Dredge each thigh in the flour, dip back in the buttermilk, then press into the flour again. Rest on a wire rack for 5 minutes.

Heat 3 inches of neutral oil in a heavy pot to 350°F (175°C). Fry 2 chicken thighs at a time for 6 to 7 minutes, turning once, until deep golden and cooked through to 165°F (74°C). Transfer to a wire rack and repeat.

Melt the butter in a small saucepan over low heat, add the Frank's RedHot and honey, and whisk for 1 minute until smooth. Toss the fried chicken in the sauce to coat and return to the rack.

Toast the brioche buns cut-side down in a dry skillet over medium heat for 90 seconds. Spread 1 tbsp mayonnaise on each bottom bun, add ¼ cup lettuce, a sauced chicken thigh, and 1 pickle slice, then top and serve.