1. Heat oven to 350 degrees F. Generously grease and flour 12-cup bundt pan.Cake:
2. On waxed paper, mix flour, baking powder, baking soda and salt. In large bowl, beat butter and sugar until smooth and light in color, 3 minutes. Add eggs, one at a time, beating well after each. With mixer running, slowly add chocolate; beat until blended.
3. On low speed, working in batches, beat in flour mixture alternately with sour cream until smooth. Scrape into pan; level top.
4. Bake in 350 degree F oven until cake tester comes out clean, about 55 minutes. Let cool in pan on wire rack 15 minutes. Invert pan; remove pan from cake. Let cake cool completely.Frosting:
5. In bowl, beat powdered sugar, butter, sour cream and vanilla extract until good spreading consistency. Cover.Shape Cake:
6. Cut cake in half to make 2 C-shaped pieces. Place half on platter to form hook of candy cane. Slice second half into 5 equal wedges. To start straight part of cane, fit a wedge up against cake half, narrow pointed end facing in, and using white frosting to attach the piece. Fit second slice up against the first, with the point of the slice facing in the opposite direction. Continue with remaining slices, using the frosting for glue.
7. Spread cake with frosting.Decoration:
8. Open red decorators icing. Using a round writing tip and flat writing tip attached to tube, alternately pipe lines over cake to create candy cane stripes.