Step 1 Preheat oven to 400°F (200°C). Whisk eggs with mustard. In separate bowl, toss ham with cheese, green onion and tomato. Divide evenly between the 24 cups of greased mini muffin tin. Pour egg mixture over top.
Step 2 Bake for 15 to 18 minutes or until eggs are set. Cool for 5 minutes. Run a thin knife around edge of each frittata to remove. Serve warm or cool completely.