Preheat the oven: Set your oven to 350°F (175°C). Grease a 12-cup muffin tin generously or line with silicone baking cups.
Prep your add-ins: Finely chop vegetables.
If using mushrooms or peppers, sauté them in a little oil for 3–4 minutes to remove excess moisture. Set aside to cool slightly.
Cook the meat (if using): Crisp bacon or brown sausage. Drain well so the cups don’t get greasy.
Whisk the egg base: In a large bowl, whisk eggs with heavy cream or almond milk.
Add salt, pepper, and any seasonings. Aim for a smooth, lightly frothy mixture.
Add cheese and mix-ins: Stir in shredded cheese, cooked meat, and veggies. Fold gently so everything is evenly distributed.
Fill the muffin tin: Divide the mixture among the cups, filling each about 3/4 full.
Give the pan a small shake to level the tops.
Bake: Place in the center of the oven and bake for 18–22 minutes, or until the centers are set and the edges are lightly golden. A toothpick should come out clean.
Cool briefly: Let them sit in the pan for 5 minutes. Run a thin knife around the edges if needed, then lift out.
Serve or store: Enjoy warm, or let cool completely before storing for later.