Preheat oven to 350 degrees.

Butter a 9 x 5 loaf pan and set aside.

Add butter and both sugars to a stand mixer with a paddle attachment.

Cream until fluffy, 2-3 minutes.

Add in eggs and vanilla.

In a large bowl combine flour, cocoa powder, baking soda and salt.

Add the dry ingredients to the wet ingredients.

On low speed add in the sour cream and mashed bananas.

Fold in the chocolate chips.

Pour the batter into the prepared pan and bake for 1 hour to 1 hour 10 minutes or until a toothpick comes out clean.

Remove from the oven and let cool in the pan for 20 minutes.

Take the loaf out of the pan and allow it to cool completely on a wire rack.

Slice bread and serve!