Preheat a grill pan over medium-high heat.
In a small bowl, combine 4 tablespoons of the melted butter with the garlic powder, onion powder, salt, and pepper.
Brush each chicken breast (halved lengthwise) with the butter-spice mixture on both sides.
Place the chicken on the preheated grill pan and cook for 3–4 minutes without moving, then flip and cook the other side 3–4 minutes.
In a medium bowl, mix 1/2 cup Parmesan with the shredded provolone until combined.
Top each chicken piece with the cheese mixture and continue cooking on the grill pan until the cheese begins to melt and the chicken reaches an internal temperature of 165°F.
Transfer the chicken to a baking sheet lined with foil.
Preheat the oven broiler on high.
In a separate bowl, combine the remaining 1/4 cup grated Parmesan with the Panko and the remaining 2 tablespoons melted butter; mix until the crumbs are evenly coated.
Evenly sprinkle the buttered Panko mixture over the top of each chicken piece.
Place the baking sheet under the broiler for 1–2 minutes, watching closely, until the breadcrumbs are golden and crispy.
Remove from the oven and let the chicken rest for 5 minutes before serving.
