While I haven't personally tried to do it this way, I can't see why you can't bake this chocolate mug cake recipe in the oven instead. Simply make sure that it is in an oven-safe dish, like a ramekin. Bake in the oven at 180ºC/350ºF for between 10-15 minutes. You can check to make sure that it is cooked through with a toothpick or skewer. I'd suggest watching it quite carefully after the 10-minute mark though as over-baked mug cake isn't great.