Preheat your oven to 350°F (175°C) and grease an 8x8 baking dish. This step ensures that your cake doesn't stick to the pan, making it easier to serve.
In a bowl, combine the all-purpose flour, whole wheat flour, baking soda, and cocoa powder. Set aside. Mixing the dry ingredients first helps ensure even distribution.
In a mixing bowl, beat together the mashed bananas, brown sugar, applesauce, and water until smooth. This creates a rich, flavorful base for your cake.
Gradually add the flour mixture to the wet ingredients, mixing until just combined. Be careful not to overmix, as this can make the cake dense.
Gently fold in 1/2 cup of chocolate chips into the batter. This step adds pockets of melted chocolate throughout the cake.
Pour the batter evenly into the greased baking dish. Use a spatula to smooth the top for even baking.
Sprinkle the remaining 1/4 cup of chocolate chips on top of the batter. This will create a beautiful, melty chocolate layer on the surface.
Bake for 30 minutes or until a toothpick inserted into the cake comes out clean. Keep an eye on it in the last few minutes to avoid overbaking.
Let the cake cool for about 30 minutes before slicing into pieces. This cooling time helps the cake set up and makes it easier to cut clean slices.
Notes
For added crunch, consider adding chopped nuts like walnuts or pecans to the batter before baking.