Use the time provided in the recipe as a guide, but remember that each microwave is different, so it will take a little bit of practice to find your perfect amount of cooking time. Once your mug cake has finished 'baking,' it should be slightly wet and sticky in the centre. If it's still completely wet, put it back in the microwave for 5 - 10 second increments until you achieve that perfect, slightly sticky consistency that will give you a fluffy cake.