Slice chicken breasts in half horizontally to create 4 thin cutlets. Pound to even thickness if needed.
In a shallow dish, whisk together flour, garlic powder, onion powder, paprika, cayenne, salt, and pepper.
Dredge each chicken cutlet in the flour mixture, shaking off excess.
Heat oil in a large skillet over medium-high heat. Cook chicken for 3-4 minutes per side until golden and cooked through (internal temp 165°F). Transfer to a plate.
In a small saucepan, combine Buffalo sauce and butter. Heat over low, stirring until butter melts and sauce is smooth.
Add cooked chicken to the sauce, turning to coat evenly.
Spread blue cheese dressing on the bottom halves of the toasted buns. Top with lettuce (if using), a Buffalo chicken cutlet, crumbled blue cheese, and sliced celery. Close with bun tops and serve immediately.
Tips
For extra crispiness, use a cast-iron skillet and avoid overcrowding the pan.
Adjust the cayenne in the flour for more or less heat.
Serve with extra blue cheese dressing and celery sticks on the side.
Leftover chicken can be stored in the fridge for up to 3 days; reheat in a skillet or oven.