1 c. butter, softened
2 c. sugar
1 c. firmly packed brown sugar
6 eggs
2 1/2 c. all purpose flour
1/4 tsp. baking soda
1/2 c. cocoa
1 (8 oz.) sour cream
2 tsp. vanilla

Beat butter at medium speed 2 minutes. Add sugar, beat medium speed 5 to 7 minutes. Add eggs, one at a time. Combine flour, baking soda, and cocoa; add to creamed mixture alternating with sour cream. Mix at lowest speed just until blended after each addition. Stir in vanilla. Spoon batter into greased and floured tube pan. Bake at 325 degrees for 1 hour 20 minutes.