Preheat oven to 350°. Combine cheeses and chilies. Place in a buttered 12x8x2-inch casserole dish. Beat egg whites until fluffy. Combine egg yolks, milk, flour, salt and pepper. Fold whites into yolk mixture. Pour egg mixture over cheese and mix slightly. Bake for 1 hour, until knife comes out clean.

Options: chop onion, green bell pepper, and red bell pepper, sauté lightly in olive oil, and combine with cheeses instead of green chilies. Or top with sliced tomatoes halfway through baking. Serve with sour cream.