Grease a microwave-safe mug or ramekin (about 3.5 inches) with olive oil.
Beat the egg and egg white with milk, salt, and pepper in a bowl until well combined.
Mix in your chosen diced vegetables or cheese.
Pour the mixture into your prepared mug.
Microwave on high for 50 seconds to 1 minute 30 seconds, until firm to touch on top.
Let it cool slightly before removing from the mug.