1. In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Add potatoes and vanilla. Combine the flour, cocoa and baking soda; gradually add to creamed mixture alternately with milk, beating well after each addition. Stir in nuts.
2. Pour into two greased and floured 9-in. round baking pans. Bake at 350°F for 25-30 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
3. For icing, in a saucepan over low heat, cook butter and brown sugar until butter is melted and mixture is smooth. Stir in evaporated milk; bring to a boil, stirring constantly. Remove from the heat; cool to room temperature. Stir in confectioners’ sugar and vanilla until smooth. Spread between layers and over top of cake. Yield: 10-12 servings.