Makes 6 egg muffins. If you are planning to feed more than six persons, cook a second batch, then keep them in the fridge to reheat when you wish. When I was testing these and had extra, we reheated them in a medium-hot skillet to serve over quinoa, with tomato salsa. Robbie suggests cutting the muffins in half and sandwiching the halves between English muffins or bread, like those at the Mcfast food restaurant.
In a large bowl, whisk the eggs, milk, salt, and pepper until just blended. Evenly divide the spinach, tomato, and scallions among the custard cups. Pour the egg mixture over the veggies. Sprinkle the Parmesan over each.
Pour 1 cup (235 ml) water into the pressure cooking pot and place a trivet in the bottom. Place 3 custard cups on the trivet and place a second trivet on top. Place the remaining 3 cups on it. Lock the lid in place. Select High Pressure and 6 minutes cook time. (see note)