Have a slightly larger cup ready. Add flour, sugar, cocoa and baking powder to the cup and stir. Then add the egg, oil, milk and Nutella. You can do it without Nutella, but it doesn`t turn out as sweet.
Mix everything well and place in the microwave for about 1 1/2 minutes, but stir again after about 20-30 seconds. If you prefer a liquid core, you can only put the cake in the microwave for about 50 seconds. Do not fall!