Preheat your oven to 375°F (190°C).
Season the steak with half of the salt and pepper, and all of the cooking oil.
Heat a cast iron skillet over high heat. Add the steak and cook for 2 minutes without stirring or flipping.
Add soy sauce and stir. Remove the steak from the pan and set aside.
In the same skillet, add butter, green bell peppers, onions, and mushrooms. Season with the remaining salt and pepper. Cook for 3-4 minutes, or until the vegetables are slightly browned.
Spread mayonnaise over both halves of the French bread.
Layer half of the sliced cheese on the bread, followed by the cooked steak and vegetables. Top with the remaining cheese.
Place the bread on the middle rack of the oven and bake for 15 minutes, or until the cheese is melted and the bread is browned.
