Sour Cream Chocolate Potato Cake

1 cup butter
2 cups sugar
2 eggs
1 cup cold mashed potatoes
1 tsp. vanilla
2 cups flour
1/3 cup cocoa
1 tsp. baking soda
1/2 tsp salt
1 cup sour cream

Brown Sugar/Caramel Icing
1/4 cup butter
1/2 cup brown sugar
2 Tbs. cream
1 3/4 cups powdered sugar
1 tsp. vanilla

In mixing bowl, cream butter and sugar until fluffy. Add eggs, one at a time, beating well after each addition. Blend in potatoes and vanilla. Combine flour, cocoa, baking soda, and salt; add alternately with sour cream; blending well after each addition. Pour into 13 x 9 inch cake pan or 2 round 9 inch pans. Bake at 350 degrees for 20 to 25 minutes or until cake tests done.
Cool on wire rack. Frost with Brown Sugar Icing.

For the Icing: Melt butter, stir in brown sugar and stir until bubbly. Remove from heat and stir in cream. Gradually add powdered sugar and vanilla. Beat by hand until frostins is spreading constistency. Immediately spread on cake.