First, preheat oven to 350°F and gather all of the ingredients.
Grease a 10"x7" or 9"x9" baking dish or cover with parchment paper.
Next, put softened butter and sugar in a mixing bowl and beat until creamy.
Add 1 egg and vanilla extract, then mix.
Peel the bananas and beat into the mixture. Then set the bowl aside.
In a new bowl, mix flour, baking soda, baking powder, and salt.
Slowly introduce the dry bowl into the creamed butter bowl, mix until smooth.
Divide the batter equally into 2 bowls.
In one bowl, add cocoa powder and mix until fully incorporated.
Spread the cocoa powder batter across the greased pan or parchment paper.
Spread remaining bowl of batter on top of the cocoa batter.
Sprinkle the top with the desired amount of chocolate chips.
Bake at 350°F for 27-35 minutes or until a toothpick comes out clean.
Let the cake cool completely before digging in.