Add dry ingredients to mug & mix well. Add the egg & mix thoroughly. Pour in the milk & oil & mix well.
Put your mug in the microwave & cook for 3 minutes (high)@1000 watts. The cake will rise over the top of the mug, but don't be alarmed! Allow to cool a little & tip it out onto a plate, if desired.
When cooled, top with whipped topping or sprinkle powered sugar over the top.