Heat oven to 375 degrees F. Add olive oil to medium nonstick, oven safe skillet over medium-high heat. Add mushrooms and onions; cook until onions are tender and mushrooms are dry. In a large bowl, whisk together eggs, egg whites, basil, parlsey, garlic ground black pepper and milk. Pour over the mushrooms and onions, stirring and shaking pan until large curds form. Smooth out the top of the frittata with a flat spatula. Sprinkle with parmesan cheese and put in oven. Bake frittata for 15-20 minutes or until set and cheese is golden brown. Remove from oven and slide frittata out of the pan onto a cutting board. Slice into 8 wedges.