Combine butter and shortening, mixing well; gradually add sugar, beating until light and fluffy. Add eggs, one at a time, beating well after each addition. Combine flour and cocoa; add to creamed mixture alternately with milk, beginning and ending with flour mixture. Mix well after each addition.
Pour batter into a well greased 10-inch tube pan. Sprinkle pecans evenly over batter. Bake at 325° for 1 hour and 15 minutes or until cake tests done, Cool in pan 15 minutes; remove from pan, and let cake cool completely.