Preheat your oven to 350°F. Grease an 8-inch square pan or line it with parchment paper.

Mix the dry ingredients in a large bowl - flour, both types of cocoa powder, baking soda, and salt.

Add the wet ingredients: water, sugar, mashed banana, coconut oil (or almond butter), and vanilla extract. Stir until just combined.

Pour the batter into your prepared pan and sprinkle mini chocolate chips on top if desired.

Bake for 25 minutes, or until a toothpick inserted in the center comes out clean.

Cool the cake in the pan for about 10 minutes, then transfer to a wire rack. Cover loosely with a towel overnight for improved texture.