Preheat the oven to 375°F (190°C). Line a baking sheet with parchment paper.

Slice the baguette in half lengthwise and place both halves on the baking sheet. In a small bowl, mix melted butter and minced garlic, then brush it evenly over the bread. Bake for 5 minutes until slightly toasted.

Heat olive oil in a large skillet over medium-high heat. Add the sliced steak and cook for 2-3 minutes until browned. Remove from the skillet and set aside.

In the same skillet, sauté the onion, bell pepper, and mushrooms (if using) until soft. Return the steak to the pan, add Worcestershire sauce, salt, and black pepper, then stir to combine.

Spoon the steak and vegetable mixture evenly over the toasted bread halves. Sprinkle shredded provolone or mozzarella cheese on top.

Bake for 10-12 minutes until the cheese is melted and bubbly. Garnish with dried parsley before slicing and serving.