In a large mixing bowl, cream butter and sugar. Add eggs, one at a time, beating well after each addition.combine the flour, baking powder and salt.combine sour cream and vanilla; add to creamed mixture alternately with dry ingredients. Combine topping ingredients; sprinkle 2 Tbsp. into a greased and flour 10 inch tube pan. For glaze, in a microwave-safe bowl, melt chocolate chips and butter; stir until smooth. Spoon half of the batter over topping; sprinkle with half of the remaining topping. Drizzle with half of the glaze. Top with remaining batter; sprinkle with remaining topping.
Bake at 350 degrees F for 60-70 minutes or until toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack. Warm remaining glaze; drizzle over coffee cake. Serve warm, if desired.