Created by CatCora on July 28, 2012
Step 1: Heat a small amount of oil or butter in a skillet. Toast the bread cut side down in the skillet until lightly toasted. Remove to a plate.
Step 2: Add peppers and onion to the pan (adding in more butter or oil if you need to). Cook 4-5 minutes, or until crisp tender (if you prefer them softer, just cook them a little longer). Remove to a bowl or plate.
Step 3: Add mushrooms to the pan and cook 5-8 minutes until golden and browned. Turn off the heat. Return peppers and onions to the pan. Toss to combine. Add in cooked beef slices then toss and heat through. Top beef/vegetable mixture with provolone slices to melt.
Step 4: Divide filling among the buns. wrap each sandwich tightly in foil and warm in a 300F oven for about 10-15 minutes. Serve warm.