In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Beat in vanilla. Combine the flour, baking powder and baking soda; add to creamed mixture alternately with sour cream, beating well after each addition. Fold in chocolate chips.
Pour into a greased and floured 10-in. fluted tube pan. Bake at 350° for 60-65 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack to cool completely.
For glaze, in a microwave-safe bowl, melt chocolate chips and butter; stir until smooth. Whisk in confectioners' sugar, milk and vanilla until smooth. Drizzle over cake. Yield: 12-14 servings.