Preheat oven to 375°F; grease a 9x13-inch dish.
Melt 2 tablespoons butter in a large skillet over medium-high; season steak with salt and pepper and cook 5-7 minutes until browned. Transfer to a plate.
Add remaining tablespoon butter; cook pepper, onion, and mushrooms about 8 minutes until softened, then garlic another minute until fragrant.
Return steak; stir in Worcestershire and cook 2 more minutes.
Mix cream cheese and broth in a medium bowl until smooth and creamy.
Spread bread evenly in dish; pour cream cheese mixture over, then top with steak and vegetables.
Cover casserole with provolone slices.
Bake 25-30 minutes until cheese melts, bubbles, and starts browning; cool 5 minutes before serving.