Grease two loaf pans. (My loaf pans are 8.5x4.5") In a small bowl, mix together 3 tablespoons of sugar and 1 teaspoon cocoa powder. Dust pans lightly with mixture. It should stick easily with the sides greased.
In a large bowl, mix butter and sugar together. Stir in eggs, mashed bananas, sour cream, and vanilla. Mix in baking soda, flour and cocoa. Then add in chocolate chips. Divide batter into the two prepared pans.
Bake for 60-65 mins.
Recipe by THE SEMISWEET SISTERS at http://www.thesemisweetsisters.com/2015/07/30/double-chocolate-banana-bread-recipe/