Cook in the microwave for 50-60 seconds. (At home, it took me 60 seconds in a 600W microwave. In the test kitchen, 55 seconds in a 1000W gave me a good result.) Too little time, and the cake will be wet on the outside. Too much time, and it will become really crumbly. Also, cooking them individually is best.
Once it's cooked, take off the plastic wrap and pop the cake out onto a plate. It should come out fairly easily, but if it needs a little help you can run a butter knife around the edges.
Eat by itself or with jam, whipped cream, ice cream, nutella, sprinkles, fresh fruit... well, anything really. I macerated some strawberries and served it with whipped cream. :D