Add the dry ingredients to a small bowl and whisk to combine well.
Add the wet ingredients to the dry, and stir to blend well.
Turn the batter into your mug (be sure to get it all.)
Microwave on high for 1 minute. Note: my microwave oven is 1200 watts. If yours is more or less than that, your exact time will vary slightly. The cake is done when it is no longer shiny and wet on top. It may just be beginning to pull away from the sides of the mug. Do not over cook!
Mix the frosting ingredients together in a small glass until lump free and glossy.
Pour the frosting over the warm cake and top with sprinkles, if desired. Enjoy!