Cream together room temperature butter and sugar with a hand mixer or with the paddle attachment of your stand mixer. Add beaten eggs and beat this mixture until smooth. Add vanilla and mashed bananas. Mix again until smooth.
Sift flour, powder, and baking soda. Add this dry mixture to the banana mixture, alternating with sour cream. (I add a scoop of dry mixture, a scoop of sour cream, and keep mixing and repeating until all ingredients are used up)
Pour half the cake batter into a greased 9 x 13 pan. Combine cinnamon and brown sugar. Sprinkle half the mixture over batter in pan. Top with half the chocolate chips. Repeat, so you have two layers of cake and two layers of the cinnamon/brown sugar/chocolate (this will be your top layer).
Bake @ 350 for 50-55 minutes, until the center of the cake is set.