Heat oven to 350 ° F. Generously grease and flour 12-cup fluted tube pan. In bowl, beat butter, sugar and vanilla until well blended. Add eggs; beat well. Stir together flour, 1 t. Baking soda and salt; add alternately to butter mixture with buttermilk. Pour 4 cups batter into prepared pan. In remaining batter, stir in topping and remaining 1/4 t. Baking soda. Spoon over vanilla batter. Sprinkle chocolate chips over surface. Bake 50 minutes or until wooden pick inserted in center comes out almost clean. Cool 10 minutes, remove from pan to wire rack. Glace with Chocolate drizzle. 12-16 servings. Drizzle: melt chocolate chips with shortening.