Chocolate "Kinder Pingui" Mug Cake

Mash the banana with a fork until smooth. Add the egg and mix well. Stir in the dry ingredients: starch, cocoa powder, baking powder, and sweetener. Mix thoroughly until uniform.

Lightly grease a tall mug with oil. Pour the batter in. Microwave for 2-3 minutes, depending on your microwave's power (two minutes was enough for me). The cake is done when it's baked through and pulls away from the edges. Be careful not to overbake! Let the cake cool completely, then cut it in half horizontally to create two layers.

Prepare the filling by combining the quark (or smooth cottage cheese) with the sweetener. Mix well.

Assemble the cake. Generously spread the filling over the bottom layer and top with the second layer. Then frost the top and sides of the cake with the remaining filling.