Cake: Preheat oven to 350° F.

Grease and flour Bundt cake pan. In a large bowl, beat butter and margarine until creamy. Add granulated sugar, and beat until light and fluffy. Add eggs, one at a time, beating well after each addition. Gradually add confectioners sugar; blend well. Stir in flour, cocoa and nuts. Stir until well blended. Pour batter into prepared pan. Bake for one hour (since this cake has a soft tunnel of fudge, an ordinary doneness test cannot be used). Cool upright in pan on a wire rack for one hour; invert onto serving plate. Cool completely.

Glaze: In a small bowl, combine all glaze ingredients until well blended. Spoon over top of cooled cake, allowing some to run down sides. Store tightly covered. Yield: One 10-inch cake.