Pound the chicken: Place each chicken breast between sheets of plastic wrap and pound to about 1/2 inch thick. This helps it cook evenly and stay juicy.
Season: Pat the chicken dry and sprinkle both sides with salt and pepper.
Set up a breading station: Put flour in one shallow dish.
Beat the eggs with milk in a second dish. In a third dish, mix breadcrumbs, Parmesan, garlic powder, onion powder, paprika, and a pinch of salt.
Bread the chicken: Dredge each breast in flour (shake off excess), dip in egg, then press into the breadcrumb mixture until well-coated. Place on a plate to rest for 5–10 minutes so the coating adheres.
Preheat and prep: Heat your oven to 400°F (200°C).
Line a sheet pan with parchment paper or lightly grease it.
Pan-sear for color: Heat oil in a large skillet over medium to medium-high heat. Sear the chicken 2–3 minutes per side until golden. You’re not cooking it through—just building color and crunch.
Transfer and top: Move the chicken to the sheet pan.
Lay 2 slices of ham on each piece, then top with a slice (or two) of Swiss cheese.
Bake: Bake 8–12 minutes, until the chicken reaches an internal temperature of 165°F (74°C) and the cheese is melted and bubbly.
Make the sauce: While the chicken bakes, whisk together mayonnaise, mustard, honey, lemon juice, salt, and pepper. Adjust sweetness and tang to taste.
Serve: Let the chicken rest 3 minutes. Spoon or drizzle honey mustard over the top, or serve on the side.
Garnish with parsley and a squeeze of lemon if you like.