Preheat the oven to 325°F. Generously spray 2 mini muffin pans with baking spray or line with mini paper muffin liners.
In a large mixing bowl, cream the butter and sugar together with an electric mixer. Blend in the sour cream, eggs and vanilla extract.
In a separate bowl, whisk together the flour, baking soda, baking powder and salt. Add the dry ingredients to the butter mixture and stir just until combined. Fold in the bananas and chocolate chips.
Spoon the batter into the prepared pans and bake for 25 to 30 minutes or until the tops are lightly golden and a toothpick comes out clean. Remove from the oven and cool on a rack for 10 minutes before unmolding.