Preheat oven to 350. Grease or spray a 13" x 9" baking dish.

In a large mixing bowl, cream together butter and sugar.

Add in egg, vanilla extract and mashed bananas - mix until well combined.

In a separate bowl, whisk together flour, baking powder, baking soda and salt.

Add flour mixture to banana mixture - mix until well combined.

Divide batter in half into two separate bowls. This doesn't have to be measured exactly, just eyeball it.

In one half, stir in chocolate chips.

In the other half, mix in cocoa powder.

Spoon cocoa batter into greased baking dish and smooth out with a spatula. Spoon chocolate chip batter on top, carefully smoothing out with a spatula.

Bake for about 25 minutes or until toothpick inserted in center comes out clean.

Cool completely on wire rack. Cut into bars and serve/ or store.