Preheat Oven: Preheat your oven to 180°C (360°F). Lightly grease a baking dish or line it with parchment paper.

Mix Wet Ingredients: In a bowl, whisk together the egg, milk, and mashed banana until smooth.

Add Dry Ingredients: Add the oatmeal, cocoa powder, and baking powder to the wet mixture. Stir until everything is well combined.

Bake: Pour the mixture into the prepared baking dish and bake for 25 minutes, or until a toothpick inserted into the center comes out clean.

Cool and Serve: Let it cool slightly before serving. Enjoy warm or at room temperature!