Preheat oven to 425° F.
Spray casserole with non-stick spray.
In medium skillet, melt margarine, add onions and mushrooms and cook over medium heat until onion is translucent.
Stir in potatoes, rosemary and pepper and transfer to casserole.
In 2-cup measuring cup, add broth packets and 2/3 cup water; pour over potatoes and top evenly with cheese. Bake, covered, 1 hour.
NOTE: Check on this a couple of times to keep pressing down the taters into the broth and keeping them moist.
Servings: 4