Easy Chocolate Banana Cake

Ingredients : 1 (18.25 ounce) package white cake mix ⅓ cup vegetable oil 4 eggs 8 ounces sour cream 8 tablespoons unsweetened cocoa powder ½ cup semisweet chocolate chips 1 banana peeled and mashed Methods : Preheat oven to 350 degrees F (175 degrees C). Lightly grease and flour one...