Preheat oven to 350º. Butter a 10” tube pan. Stir together crumb mixture in small bowl. Set aside. Sift flour, cocoa powder, baking powder, baking soda and salt into a medium bowl, set aside.
Beat butter an sugar until light medium bowl with electric mixer at high speed. Lower mixer speed to medium, add vanilla and then eggs at one at a time, beating well after each addition. Blend in sur cream. Lower mixer to slow, beat in flour mixture until just blended.
Spread ½ of batter in pan, sprinkle with ½ of crumb mixture, top with remaining batter. Swirl batter gently with a knife in up and down motion. Tap pan to settle ingredients. Bake 40 min. Cover with foil and bake an additional 20 minutes or until a pick in center comes up clean. Cool in pan for ½ hour, before placing on wire rack