In a large skillet over medium heat, stir mushrooms and gravy till warm.
Stir in lowfat sour cream till smooth.
Add in roast beef slices and cook till heated through.
Top each slice of bread with two roast beef slices and some gravy.
Yield: 4 servings
This is a recipe I made up for my web site feature on Planned Leftovers There are additional recipes, leftover tips, links to recipe collections and more on which page.