Preheat oven to 350 F. Grease and flour a 10-inch bundt pan. Cream the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Beat in the vanilla extract.
Add the bananas and beat just until incorporated. Combine flour, baking powder, baking soda and salt. Add this dry mixture to the batter in the bowl, alternately with the sour cream. Beat just until the ingredients are incorporated. Mix in the walnuts and chocolate chips.
Pour the batter in the greased bundt pan and bake at 350 F for 50-55 minutes.