Place the butter in your mug or ramekin and microwave for about 15 seconds so it melts. Put in the egg and milk and mix with a fork. Add in the banana and mix until its combined. Add in the dry ingredients an mix with your fork until just combined.
Cook in the microwave for 2 minutes and 30 seconds on medium power. If its still gooey in the middle cook in 10 second increments until done. Serve warm with ice cream.
Recipe by Reality Daydream at https://realitydaydream.com/single-serving-banana-mug-cake/