Step #5 Remove vegetable mixture from heat, & transfer to a plate to cool briefly.
Step #6 Wipe pan with paper towels, & return to stove.
Step #7 Combine eggs, milk, egg whites, & basil In a large-ish bowl, salt, pepper, stirring with a whisk until well mixed; set aside.
Step #8 Heat skillet over med-heat/flame for 2-3 mins & add butter, swirling pan to melt butter evenly.
Step #9 Add vegetables to egg mixture in bowl, stir, & carefully pour entire mixture into heated skillet.
Step #10 Scatter cherry tomatoes & cheese over egg mixture (do not stir).
Step #11 Cook frittata carefully over medium-low heat 15-18 mins or untilit is cooked most of the way through.
Step #12 To finish cooking the top, preheat broiler & place the frittata about 6-8 inches from heat for 2-4 mins (watch frittata carefully to ensure that it doesn't burn).
Step #13 Remove frittata from oven, cool on a wire rack for 5 mins, & shake pan rapidly back & forth to loosen.
Step #14 Cool a few more mins, then carefully put a plate over the frittata & invert it onto the plate.
Step #15 Invert it again onto another plate so the frittata is right side up.
Step #16 Refrigerate until ready to serve.
Enjoy the Mushroom, Pepper, & Fontina Frittata recipe