Preheat your oven to 375°F (190°C) and prepare a 12-cup muffin pan with cooking spray.

Slice 2 cups of mushrooms and roughly chop 2 cups of fresh spinach.

Sauté the sliced mushrooms in a skillet over medium-high heat for 2–3 minutes until browned.

Add the chopped spinach to the skillet and cook for another minute until wilts down.

In a mixing bowl, beat together 4 large eggs, then whisk in 1/4 cup Parmesan, 2 tbsp milk, garlic powder, onion powder, salt, and black pepper.

Fold the cooled mushroom and spinach mixture into the egg mixture.

Pour the quiche mixture into the prepared muffin cups, filling each about 3/4 full.

Bake for 18–20 minutes or until they are set in the center and spring back when touched.

Allow muffins to cool in the pan for about 5 minutes before transferring to a wire rack.