Preheat oven to 200°C
Whisk eggs with mustard and self-raising flour.
In separate bowl, toss ham with cheese, red onion and tomato.
Divide evenly between the 24 cups of greased mini muffin tin. Pour egg mixture over top.
Bake for 15 to 18 minutes or until eggs are set.
Cool for 5 minutes. Run a thin knife around edge of each quiche to remove from tin. Serve warm or cold for a delicious snack for any time of day.