In a skillet over medium high heat, add olive oil. When warm add the onions, peppers & mushrooms. Sautée for approximately 6 minutes, tossing mixture a few times as it cooks. When done put mixture aside on a dish for later.
Toast grinder rolls in oven/toaster or in another pan with butter.
In the skillet over medium high heat add butter. As butter is melting add the shaved steak pulling it apart as you put it in and spreading it out covering the entire skillet. Add garlic, salt and pepper. Sautée for about 2 minutes and then flip steak over and go another minute until pink color is gone.
Add pepper/onion/mushroom mixture back into the skillet and mix up together with the steak. Turn off heat and add slices of cheese on top and let melt for approximately 2 minutes. When cheese is melted, split portions and fill warm grinder rolls.
