What You Need
PreparationHeat 2 tablespoons of the oil in a 12" HexClad Hybrid Pan over medium-high heat. Add the onion and mushroom and cook until light golden, about 7 minutes. Add the peppers, garlic, and rosemary, 3 more minutes. Season with salt and pepper. Scrape into a bowl , discard rosemary, and wipe out pan.
Return the pan to medium-high heat. Add another tablespoon oil and half of the beef and cook, tossing occasionally, until cooked through and light golden, about 4 minutes. Return half of mushroom mixture to the pan and toss to combine and heat through. Top with 3 slices of provolone cheese and add a splash of water to the skillet. Cover and cook, just until the cheese is melted, about 1 minute.
Scoop into submarine sandwich and drizzle with some ketchup. Repeat with remaining oil, beef, mushroom mixture, and submarine sandwich.