1. Preheat oven to 350°F and spray 12-cup muffin tin generously with cooking spray – get bottoms AND sides! This is crucial. Set out all mix-in ingredients so you’re ready once egg mixture is prepared.

2. Crack all 12 eggs into large bowl. Add milk, salt, pepper, and garlic powder if using. Whisk everything together really well – about 30-45 seconds. You want it completely smooth with no streaks of egg white. Taste and add more salt if needed.

3. Have all chosen ingredients diced into small, bite-sized pieces. If using watery vegetables like tomatoes or mushrooms, cook briefly first and pat dry. Cooked meats should be room temperature. Cheese should be shredded.

4. Either mix all chosen ingredients into egg mixture and divide evenly, OR add different combinations to each muffin for variety. You can put a little of each ingredient directly into each cup, then pour egg over top. This ensures every muffin gets good distribution.

5. Pour egg mixture into each muffin cup, filling about three-quarters full. Eggs will puff up as they bake, so you need that room. If you put mix-ins directly in cups, use fork to gently stir each one to distribute evenly.

6. Bake for 20-25 minutes until muffins are puffed, golden around edges, and set in center. They should spring back when gently pressed. Toothpick inserted in center should come out clean.

7. Let cool in pan for 5 minutes – crucial step! If you try to remove immediately, they’ll stick and fall apart. After 5 minutes, run butter knife around edge of each muffin and gently lift out. They’ll deflate slightly as they cool, which is normal.