Place each chicken breast half between two sheets of plastic wrap and pound to an even 1/2-inch thickness.
In a large bowl, whisk together 1½ cups buttermilk, 1 Tbsp hot sauce, 1 tsp salt, 1 tsp black pepper, 1 tsp onion powder, and 1 tsp garlic powder to make the marinade.
Add the chicken cutlets to the marinade, turn to coat, cover, and refrigerate for 2–4 hours or overnight.
In a separate shallow bowl, combine 1½ cups all-purpose flour, 2 tsp salt, 1 tsp freshly ground black pepper, 1 tsp baking powder, 1 tsp paprika, 1 tsp onion powder, and 1 tsp garlic powder for the breading.
Remove a piece of chicken from the marinade, let excess drip off, and press into the flour mixture to coat well. Place coated pieces on a wire rack. Just before frying, dredge each piece in the flour mixture again for a thicker, shaggy crust.
Heat about 1 inch of oil in a large pot or Dutch oven to 350°F (175°C). Reduce heat slightly so the oil stays around 300–325°F while frying.
Carefully lower chicken into the oil, 2 pieces at a time for a smaller pot, without crowding. Fry 3–4 minutes on the first side until browned and crisp, then flip and fry 2–3 minutes more until cooked through and golden on both sides.
Transfer fried chicken to a wire rack set over a baking sheet to drain and rest; final internal temperature should reach 165°F.
Lightly butter and toast the bun cut sides. Assemble sandwiches with mayonnaise (or sauce), lettuce, tomato slices, pickles, and the fried chicken.
