Heat milk in large saucepan. Stir in butter or margarine until melted. Gradually stir in corn meal. Cook over medium heat until mixture boils. Cook, stirring constantly, 1 minute longer. Remove from heat and cool slightly. Stir egg yolks into corn meal mixture until well blended. Beat egg whites until stiff, but not dry, peaks form. Fold into corn meal mixture. Turn into well greased 2 quart casserole dish. Bake in preheated 350 degree oven for 45-50 minutes or until deep golden brown. Serve immediately.