Preheat oven to 350 F. Spray a loaf pan with non stick spray.

In a large bowl, mix butter and sugar until creamy. Add eggs and vanilla and mix well.

In a seperate bowl, combine all of the dry ingredients. Add to the wet mixture in two batches, mixing well after each addition.

Add sour cream and bananas and mix well.

Using a rubber spatula, fold in chocolate chips.

Pour into prepared loaf pan, about 3/4 full.

Bake for 1 hour and 20 minutes.