Place chicken breasts in a zip-top bag and, if needed, slice each breast horizontally to make thinner cutlets. Use a meat mallet to gently pound each piece to an even 1/2-inch thickness.
In a pie plate, whisk together the flour, salt, and black pepper; stir in about 3 tablespoons of the buttermilk so the mixture is slightly shaggy.
Pour the remaining buttermilk into a second shallow dish.
Pat each chicken piece dry, dip into the buttermilk, shake off excess, then dredge in the seasoned flour, coating both sides. Set the coated chicken on a wire rack and let rest 5 minutes.
Fill a heavy-bottomed pot with vegetable oil to about 3 inches deep and heat to 350°F (175°C).
Fry the chicken in batches (2–3 pieces at a time) for 4–5 minutes, or until an instant-read thermometer registers 165°F (74°C). Transfer cooked chicken to a clean wire rack.
Make the Buffalo sauce by combining Worcestershire sauce, Frank's RedHot, and 1/4 cup softened butter in a small saucepan over medium heat; stir until butter is melted and sauce is smooth.
Brush a small amount of softened butter inside the hamburger buns and place them under the broiler until golden brown—watch closely to avoid burning.
Place the fried chicken in a bowl, pour the Buffalo sauce over it, and toss until each piece is evenly coated.
Assemble sandwiches by placing a sauced chicken breast on each bottom bun, topping with 4 dill pickle slices, then covering with the top bun.
