Sweet Potato Chocolate Cake - cooking recipe

Ingredients

3/4 cup butter
2 cups sugar
4 eggs, separated
1 cup sweet potato, cooked and mashed
1/2 cup water
1 teaspoon vanilla
2 cups all-purpose flour
3 tablespoons baking cocoa
2 teaspoons baking powder
1 cup chopped walnuts
1 (15 5/8 ounce) container chocolate frosting

Preparation

In a large bowl, cream together the butter and sugar. Add the egg yolks, sweet potatoes, water, and vanilla. Mix well.
In another bowl, combine the flour, cocoa, and baking powder. Add to the sweet potato mixture.
Beat the egg whiltes until they form stiff peaks. Fold the egg whites and nuts into the batter. Pour into a greased 9x13 baking dish. Bake at 350 degrees for 30-35 minutes.
Allow to cool completely before frosting.