Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish and set aside. If your steak is not already shaved, slice it as thinly as possible against the grain. Slice the onion, bell pepper, and mushrooms (if using). Cut hoagie rolls into 1-inch cubes and toss with melted butter in a small bowl; set aside.

Heat 1 tablespoon of olive oil in a large skillet or Dutch oven over medium-high heat. Add the thinly sliced steak in batches, if necessary, to avoid overcrowding. Cook quickly for 2-3 minutes per batch until browned. Season with a pinch of salt and pepper. Remove steak from the skillet and set aside on a plate.

Add the remaining 1 tablespoon of olive oil to the same skillet. Reduce heat to medium. Add the sliced onions, bell pepper, and mushrooms (if using). Sauté for 8-10 minutes, stirring occasionally, until vegetables are tender and slightly caramelized. Stir in garlic powder, onion powder, salt, and pepper during the last minute of cooking.

Push the cooked vegetables to one side of the skillet. Add the softened cream cheese, sour cream, beef broth, and Worcestershire sauce to the empty side of the skillet. Stir and melt the cream cheese, mixing it with the other liquid ingredients to form a smooth, creamy sauce. Once smooth, stir the sauce into the vegetables until everything is well combined.

Return the cooked steak to the skillet with the vegetable and cheese sauce mixture. Stir gently to combine all ingredients.

Pour the entire mixture into the prepared 9x13 inch baking dish, spreading it evenly.

Arrange the provolone cheese slices over the top of the casserole. Sprinkle generously with shredded mozzarella cheese. Finally, scatter the buttered hoagie bread cubes over the cheese layer.

Bake for 20-25 minutes, or until the casserole is bubbly around the edges and the cheese is melted and golden brown. The bread cubes should be lightly toasted and crunchy.

Remove from oven and let the casserole rest for 5-10 minutes before serving. This allows the sauce to set slightly.