½ cup butter, softened
1 cup white sugar
1 teaspoon vanilla
1 ½ cups bananas, mashed
1 ½ cups all-purpose flour
1 teaspoon baking soda
1 teaspoon baking powder
½ teaspoon salt
¼ cup unsweetened cocoa powder
- Grease a 9 x 13 baking pan and set oven to 350°.
- Beat together butter and sugar until light and fluffy. Add in egg and vanilla and mix until well combined. Fold in mashed banana and set aside.
- In separate bowl, mix together flour, baking soda, baking powder and salt. Make well in center of mixture and pour banana mixture into well. Stir until just mixed.
- Remove half the batter. Stir cocoa powder into remaining batter.
- Pour cocoa mixture into pan. Spoon plain batter on top using a knife to create a marble design.
- Bake for 25 minutes, until edges of bars are golden.