Prep the pan: Heat the oven to 350°F (175°C).
Grease a 12-cup muffin tin well with oil or use parchment liners. Greasing thoroughly is key to prevent sticking.
Beat the eggs: In a large bowl, whisk 10–12 eggs with the milk, 1/2 teaspoon salt, and 1/4 teaspoon black pepper until smooth and slightly frothy.
Cook heavier veggies: If using mushrooms, onions, or sausage, sauté them in a little oil until tender and most moisture is gone. This helps the muffins set and avoids sogginess.
Layer the fillings: Divide your chosen fillings among the cups. Aim for about 2–3 tablespoons of mix-ins per muffin.
Don’t overpack.
Add cheese last: Sprinkle cheese over fillings in each cup so it melts evenly and helps bind everything.
Pour the eggs: Fill each muffin cup about 3/4 full with the egg mixture. Stir the bowl between pours to keep ingredients suspended.
Bake: Place on the center rack and bake 18–22 minutes, or until the muffins are set in the middle and just lightly golden on top. They may puff and then settle—totally normal.
Cool and release: Let them cool in the pan for 5 minutes, then run a thin spatula around the edges to loosen.
Transfer to a rack to finish cooling.
Season to finish: Add a pinch of salt, cracked pepper, or hot sauce on top, if you like.