Mix all ingredients together with 2 tablespoons of chocolate sprinkles and stir with a whisk. Pour the dough into two cups and then place in the microwave for approx. 1 - 2 minutes at 600 W.
If necessary, sprinkle the cakes with the remaining crumble or powdered sugar.
TIP: This recipe is for 2 cups! I know from experience that it overflows in a mug in the microwave because of the baking soda!