My husband loves to eat leftover steak, cold, sliced thin and salted. But to me this sandwich is far and away the best thing to do with leftover steak. The recipe, Philly-Style Mushroom Cheesesteak, from Fine Cooking issue #47, starts with cooking a steak intentionally to make this sandwich. But I just pick up midway and use leftover steak. You saute mushrooms, onions and garlic until soft and then toss in a few cherry tomatoes and thin-sliced cooked steak. You heat it through, divide it into two portions on opposite sides of the pan and melt some provolone over each pile of steak and vegs. After it melts, use a big flat spatula to move the whole mess to a slice of toasted french bread. This is knife and fork food at its best. However, I'm quite sure it is nothing like an authentic Philly Cheese Steak.