5.

Microwave for 3 minutes in a 1000 watt microwave, or 4 minutes in a 700 watt oven. The cake will puff up in the mug while it bakes, but don't panic--it will deflate when you remove it from the heat. Note: If you are worried about spillage, or if you are using a smaller mug and it is looking pretty full, err on the side of caution and put a plate beneath the mug--this will save you possible cleanup woes later.