1 pound sweet potatoes (about 4 medium ones)
3 egg whites (or 1/3 cup nonfat egg substitute)
1/2 cup sugar
1 10 ounce can evaporated skim milk
1 tablespoon vanilla extract
1 teaspoon cinnamon
1/2 teaspoon nutmeg
1/2 teaspoon ginger
Rinse sweet potatoes in cold running water and pierce with a fork. Microwave on full power until tender, about 15 minutes. Turn them half way during baking.
Preheat oven to 400 degrees. Remove skin from sweet potatoes and mash with hand beaters or food processor. Add the rest of the ingredients and mix smooth.
Pour mixture in an 8 inch square baking pan. Bake until casserole is firm in the center, about 40 minutes. Remove from oven. Allow to stand for 5 minutes then cut in 10 squares. Serve hot. Refrigerate leftovers.