Soften gelatin in 1/4 skim milk; set aside. Combine remaining 1 cup milk, egg yolks and salt in double boiler; heat until mixture coats spoon. Remove from Heat. Add gelatin mixture and sugar substitute; stir until blended. Cool. Add vanilla and half-and-half. Freeze until firm. Beat egg whites until stiff peaks form. Remove cream mixture from freezer, and place in chilled bowl; beat until smooth. Fold in stiffly beaten egg whites. Return to Freezer until ready to serve.