Liquefy the chocolate and nut spread of your choice in the microwave for about 30 seconds at 900 watts. Add the flour and stir briefly, then add the egg and work in. Grease a cup or ovenproof dish with butter and pour in the batter. Now cook in the microwave for about 90 seconds at 900 watts. If you want the cake to be a little more liquid inside, 60 seconds are usually enough.
Alternatively, it can also be prepared well in the oven, where the crust on top becomes a little crispy. Here you should preheat the oven to 180 degrees and check it for the first time after 10 minutes. As soon as the cake detaches from the edge and the crust is already in place, it should still be liquid inside, but ready.
Made ultra quick and not that cute.
If there is a Nutella deficiency, you can also replace the Nutella with 100 g butter, 50 g sugar and 80 g chocolate.