Preheat oven to 425°F. Lightly oil a sheet pan or heat an oven-safe skillet.
Pound chicken to about 1/2-inch thickness and pat dry with paper towels.
Stir mayonnaise, Dijon, lemon juice, and half the garlic powder in a bowl.
Season chicken with half the salt and pepper. Brush on a thin mayo mixture coat.
Combine Parmesan, panko, Italian seasoning, remaining garlic powder, paprika, and remaining salt and pepper.
Press chicken into crumb mixture to coat both sides, gently packing crumbs on.
Heat olive oil and butter over medium-high. Sear chicken 2–3 minutes per side until golden.
Transfer to oven and bake 8–10 minutes, until 165°F inside. Rest 5 minutes, then garnish with parsley.