Spinach Frittatini

1. Peel and quarter the onion.
2. Attach the slicer/grater to the food processor. Chop the onion on speed 4.
3. Heat the olive oil in a large skillet over medium-high heat.
4. Add the onions and sauté for about 2 minutes, until they become slightly soft and translucent.
5. Add the spinach and sauté for one minute. Remove the onions and spinach from the heat and let them cool.
6. Using the slicer/grater attachment, grate the cheddar at speed 4 into a bowl. Add the eggs, milk, salt, and chives.
7. Mix on speed 4 for 90 seconds in a food processor fitted with a wire whisk. Add the onions and spinach and mix at an appropriate speed until the ingredients are well combined.
8. Grease a 6-cup muffin pan and spoon a generous tablespoon of the egg mixture into each cup.
9. Bake in a preheated oven at 170 °C for 20 minutes until the center of the frittatas is set.