Preheat the broiler and set the rack about 4 to 5 inches from the heat source.
Heat oil in large ovenproof nonstick skillet over medium-high heat.
Saute mushrooms until browned, seasoning with salt and pepper.
Add onion and saute until tender.
Whisk eggs, egg whites, salt, and pepper in a medium bowl.
Pour over vegetables in skillet and mix gently. Reduce heat to medium-low, cover skillet, and cook until eggs are set around edges, about 4 to 5 minutes.
Sprinkle with cheese and then place skillet under broiler and cook until cheese is melted and just browned, about 2 minutes.
Let frittata stand 1 minute before cutting into 8 wedges.
Serve with salad on the side.
large bunch arugula leaves, washed and dried
/4 cup olive oil
lemon, juiced
grinds black pepper
Couple pinches salt
Combine all ingredients in a large bowl. Toss to coat leaves with dressing and serve with the frittata.