Chocolate Potato Cake

Description
Here's one of my favorite cake recipes.
 * Contributed by Joanne at Catsrecipes Y-Group
 * Makes 10 servings

Ingredients

 * 1 cup butter or margarine, softened
 * 2 cups granulated sugar
 * 4 eggs
 * 2 squares unsweetened chocolate, melted
 * 1 teaspoon vanilla extract
 * 1 cup cold mashed potatoes
 * 2 cups sifted all-purpose flour
 * 1 teaspoon baking soda
 * ½ teaspoon salt
 * ¾ cup sour milk or buttermilk

Directions

 * 1) In large bowl, with electric mixer at medium-high speed, cream together butter or margarine and sugar.
 * 2) Beat in eggs, one at a time, melted chocolate and vanilla extract until blended.
 * 3) Reduce speed; stir in potatoes and mix well.
 * 4) Onto wax paper, sift together flour, baking soda and salt.
 * 5) Add to batter alternately with sour milk or buttermilk, blending well after each addition.
 * 6) Pour into 3 greased 9-inch cake pans (or one 9-inch tube pan).
 * 7) Bake in a preheated 375°F oven for 20 minutes for 9-inch cake pans; 1 hour for 9-inch tube pan; or until cake tester inserted in center comes out clean.
 * 8) Cool cake 10 minutes; remove from pans to wire racks to cool completely.
 * 9) Fill and frost cake with your favorite frosting.