Grease a mug with butter, then crack eggs into it and mix together well with a fork.
Add in the cooked ham, cheese, and spring onion.
Season with salt and pepper and stir to combine.
Microwave on high for 90 seconds. If the egg is not cooked enough, microwave in 10-15 second intervals until cooked through. Do this carefully as the eggs can become rubbery if overcooked.