makes it silkier and richer than milk, like quiche. But milk works just fine! Full fat better than light but light is also just fine.
2. Vegetable switch outs:
5 to 7 cups of any roastable vegetables of choice, OR anything else you want to put in: cooked chicken, flaked salmon (fresh or canned), ham, antipasto type things (olives, chargrilled peppers, artichokes).
3. Pan size -
don't get too hung up about pan size, if your pan is smaller then make yours a rdeep dish frittata. If there's overflow, stop pouring egg mixture in and put the leftover in a ramekin. OR use the recipe scaler (tap /click servings and slide down) - for a 20cm/8" square pan, slide down to 8 eggs.
Just don't use a pan that's much larger otherwise your frittata will be disappointingly thin.
per slice, 8 servings (pretty decent size piece).