Recipe Banana Fudge Cake

Ingredients
1 (18.25 ounce) package chocolate fudge cake mix
1 large ripe banana, mashed
FROSTING:
1/2 cup butter or margarine
1/4 cup water
5 1/2 cups confectioners' sugar, divided
1/4 cup baking cocoa
1 small ripe banana, mashed
1/2 teaspoon vanilla extract

Directions
In a mixing bowl, prepare cake mix according to package directions, omitting 1/4 cup of the water. Beat on low speed until moistened. Add banana; beat on high for 2 minutes. Pour into a greased 13-in. x 9-in. x 2-in. baking pan. Bake at 350 degrees F for 35-40 minutes or until a toothpick inserted near the center comes out clean. Cool completely. In a saucepan, heat butter and water until butter is melted; set aside. In a mixing bowl, combine 4 cups confectioners' sugar and cocoa. Add butter mixture, banana and vanilla; beat until smooth. Add enough remaining sugar until frosting reaches desired spreading consistency. Frost the cake.