Panko is the key to these delicious baked chicken sandwiches. Try ranch dressing in place of the blue cheese and mayonnaise if you like.
Preheat oven to 425 degrees. Toss panko with butter and 1/2 teaspoon salt on a rimmed baking sheet. Toast in oven, stirring twice, until golden brown, about 6 minutes; let cool 10 minutes. In a shallow dish, whisk together mayonnaise and hot sauce. Season chicken with salt and pepper, then dredge in flour, tapping off excess. Dip in mayonnaise mixture; coat with panko, patting to adhere. Transfer to another rimmed baking sheet.
Roast chicken, flipping once, until cooked through, about 12 minutes. Let cool slightly. Slice cutlets in half crosswise and place, stacked, on bottom buns. Add cheese, celery, lettuce, mayonnaise, and hot sauce; sandwich with top buns. Serve, with chips.