Preheat your oven to 400.
Spray a small skillet with cooking spray. Arrange the English muffin chunks in the skillet.
In another medium bowl, whisk together the eggs, milk, cheese and mustard. Season with a pinch of salt and pepper. Pour the mixture right over the muffin pieces, submerging each piece in the egg mixture.
Tuck the spinach leaves in the egg mix, and sprinkle the red onion right on top.
Bake for 30 minutes, until the eggs are set and the cheese is starting to bubble on top.
Grate some parmesan on top for extra amazingness, and serve it up!
Makes four small servings. Or two bigger ones. Or one obnoxious one. YOU DO YOU.
