1medium red bell pepper, seeded and cut into 1-inch pieces
1medium green bell pepper, seeded and cut into 1-inch pieces
1medium sweet onion, sliced
8ouncescrimini or white button mushrooms, sliced
4 8-inchhoagie rolls, see recipe notes
Preheat the oven to 400°F and line a baking sheet with parchment paper. Slice the hoagie rolls and set aside.
Trim the steak of any excess fat and cut across the grain into 1/8-inch thick slices. In a medium mixing bowl, whisk about 1-1/2 tablespoons of the olive oil together with the balsamic vinegar and garlic. Add the steak slices and toss to combine. Season with about 1/2 teaspoon of salt and a few grinds of black pepper, toss again and set aside.
Arrange the red and green peppers on the prepared baking sheet and sprinkle with salt and pepper. Roast for 8 to 10 minutes, just until they are soft and slightly caramelized. Remove from the oven and set aside.
While the peppers roast, film the bottom of an oven-proof skillet with olive oil and heat over medium heat. Add the onions and sauté until soft and translucent, 2 to 3 minutes. Add the mushrooms, season with salt and pepper and sauté until any moisture given off by the mushrooms has evaporated and they've begun to brown, 3 to 4 minutes. Transfer the mixture to a plate and set aside.
Add a little more olive oil to the pan and raise the heat to medium-high. Add the steak and fry, stirring constantly, until it reaches the desired doneness. Two minutes should be about right for medium-rare. Add the roasted peppers and onion-mushroom mixture and combine well. Taste and adjust the seasoning if needed.
Cover the steak and veggies with a single layer of cheese slices. Place the pan in the oven until the cheese has melted into the steak and veggies, 3 to 4 minutes.
To serve, spoon equal portions of the steak mixture into the rolls and serve immediately.
Tips for Making This Recipe
If possible, choose soft, Italian-style torpedo or hoagie rolls that have a light center and chewy exterior crust. This style of roll soaks up the juices from the steak without getting soggy too quickly.