Step 1

In a large bowl, cream butter and sugar until light and fluffy, 5-7 minutes. Add eggs, 1 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.

Step 2

Pour into 2 greased and floured 9-in. round baking pans. Bake at 350° until a toothpick inserted in the center comes out clean, 25-30 minutes. Cool for 10 minutes before removing from pans to wire racks to cool completely.

Step 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.