Grease the inside of your microwave-safe mug with a little butter, coconut oil or ghee.
Combine all base ingredients in a small bowl or directly in your oven/microwave safe mug.
If using a bowl, transfer the mixed ingredients to your mug.
Microwave for 1 minute. Use a toothpick or a knife to check that the mug cake is cooked all the way through.
If not done, cook for another 30 seconds, or until done.
Remove and allow to cool for 5 minutes.
Top with zero sugar whipped cream and additional pumpkin pie spice.
