Mash the banana.
Add the egg to a bowl (that can be used in the micro).
Stir and add oatmeal.
Add the mashed banana.
Stir again. If you like some sweetener, add 1/2 tsp of agave syrup.
Add baking powder and milk - feel free to use regular milk or from plants like coconut or almond milk.
..and after. I cooked mine for 1 min & 20 sec. The mug becomes very hot so turn the mug cake upside down into another bowl to make it easier to eat it.
Serve with sliced bananas or whatever you prefer. Mine was a bit runny in the middle but since it was also a little burnt on the edges (due to an old micro) I decided to eat it like this.
Enjoy your (chocolate flavored) breakfast!