Put butter into mug and microwave for 10 seconds to melt.
Add in egg and milk and lightly beat with a fork until combined.
Add dry ingredients into mug and beat with your fork until mixed through.
Place mug in the microwave and cook for 1 minute on medium heat.
The pudding should be risen and still slightly gooey in the middle. If still undercooked for your liking, cook it further in 10 second bursts in the microwave.
Serve with lightly whipped cream or icecream.
Enjoy! See below for some flavour options.