Step #1
Preheat oven to 350 degrees F (175 degrees C).
Step #2 Butter a 10 inch tube pan.
Step #3 Sift together the flour, cocoa, baking powder, baking soda, 1 tsp cinnamon, & salt; set aside.
Step #4 In a medium bowl, beat the butter & 1 1/4 c sugar with an electric mixer on high speed until light & fluffy.
Step #5 Change the mixer speed to medium, & beat in the vanilla.
Step #6 Beat in the eggs, one at a time.
Step #7 With the mixer on lowish speed, alternately beat the flour mixture & sour cream into the creamed mixture, beginning & ending with the flour mixture.
Step #8 Beat only until just mixed.
Step #9 For the topping: In a small bowl mix the chocolate, pecans, 1/4 c sugar, & 1 tsp cinnamon to make a crumb mixture.
Step #10 Spread half of the batter in the bottom of the prepared pan.
Step #11 Sprinkle top with half of the crumb mixture.
Step #12 Pour in the remaining batter, & sprinkle with the remaining crumb mixture; press the crumbs in lightly so they adhere to the batter.
Step #13 Quickly, but carefully cut through the batter & crumbs in an up & down motion with a knife.
Step #14 Lightly rap the pan once against a hard surface, to settle the batter.
Step #15 Bake in the preheated oven for 40 mins.
Step #16 Cover the top of the cake with aluminum foil.
Step #17 Continue baking until a skewer inserted halfway between the side of the pan & the tube comes out clean, about 20 mins longer.
Step #18 Cool the cake in the pan on a wire rack for 30 mins.
Step #19 Carefully loosen the cake from the sides of the pan.