Preheat your oven to 350°F (175°C). Lightly grease an 8-inch square pan or line it with parchment paper.

Sift together the flour, unsweetened cocoa powder, baking soda, and salt in a large mixing bowl.

Gradually add the water, sugar, mashed banana, and melted coconut oil or almond butter to the dry mixture and stir gently.

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

Bake in the center of the preheated oven for 25 minutes until a toothpick comes out clean.

Let the cake cool in the pan for about 10 minutes, then cover loosely and let rest overnight for better flavor.