Cook fresh asparagus, mushrooms, and green onion in a small amount of boiling water about 7 minutes or till tender. (Or cook frozen asparagus, mushrooms, and green onion according to asparagus package directions.) Drain. In a large mixing bowl combine eggs, milk, salt, nutmeg, and pepper. Beat with fork or rotary beater till blended. Stir in cooked vegetables and Swiss or Gruyere cheese. Turn egg mixture into a greased 10x6x2 baking dish. Bake, uncovered, in a 375 degree oven for 20 to 25 minutes or till set. Sprinkle with snipped parsley, if desired. Serves 4. Note: You can mix it up the night before, put in the pan and chill, and just pop it in the oven the next morning.