Soak gelatin in cold water. Put sugar, salt, egg, yolks, and Grand Marnier into top part of a double boiler. Heat and beat with a whisk, or hand mixer, until mixture triples in volume. When it starts to go down, add the
soaked gelatin. Beat until gelatin is dissolved and then add Kirsch. Remove from heat, set into ice water, beat, and cool until it starts to set.