Preheat oven to 300°F. Grease 10-inch Bundt pan. Set aside.

Sift flour into medium bowl. Sift again with cocoa, baking powder and salt.

Beat margarine and shortening 1 minute in large bowl with electric mixer at medium speed. Beat in sugar gradually. Add eggs, one at a time, beating well after each addition until blended. Add flour mixture, milk and vanilla; mix well. Pour into prepared pan.

Bake 1 hour or until toothpick inserted into center comes out clean. Cool cake completely in pan on wire rack. Prepare Chocolate Frosting. Invert cake onto serving plate. Frost top and sides of cake with frosting.

Combine milk and chocolate in medium saucepan. Cook over low heat, stirring constantly, until almost thickened. Add sugar; bring to a boil. Boil 9 to 10 minutes, stirring constantly. Add butter and salt; remove from heat. Cool 20 minutes. Add vanilla; beat until spreadable.