Start by pounding the chicken breasts to an even thickness, about ½ inch thick. This helps the chicken cook evenly and ensures a tender sandwich.
Place the pounded chicken breasts in a shallow dish and pour buttermilk over them. Make sure the chicken is fully coated. Cover the dish and let it marinate in the refrigerator for at least 30 minutes, or up to 4 hours for maximum flavor.
In a separate shallow dish, mix together the flour, paprika, garlic powder, onion powder, cayenne pepper, salt, and pepper. This will be the coating for your chicken.
Remove the chicken from the buttermilk marinade, allowing any excess to drip off. Dredge the chicken breasts in the seasoned flour mixture, making sure they are evenly coated on all sides.
In a large skillet or deep fryer, heat vegetable oil to 350°F (175°C). You'll need enough oil to submerge the chicken breasts halfway.
Carefully place the coated chicken breasts into the hot oil. Fry for about 5-6 minutes per side, or until golden brown and cooked through. The internal temperature of the chicken should reach 165°F (75°C).
While the chicken is frying, toast the hamburger buns if desired. Once the chicken is done, remove it from the oil and place it on a paper towel-lined plate to drain any excess oil.
Spread spicy mayonnaise or your favorite hot sauce on the bottom half of each bun. Top with lettuce, tomato, pickles, and the fried chicken breast. Add the top half of the bun and serve hot.