In large bowl, with an electric mixer, cream butter & sugar. Add eggs one at a time, beating well after each addition. Add vanilla & bananas, mixing until smooth.
In another bowl, combine flour, baking powder, & baking soda. Add to the banana mixture alternately with sour cream, ending with the dry ingredients.
Spread half of the batter into a greased 9x13" baking pan. Combine cinnamon and brown sugar, sprinkle 1/2 of this mixture over batter, then 1/2 the chocolate chips. Repeat layers. Bake in preheated 350° oven for 50 - 60 minutes. Makes 16 servings.