Prepare cake as directed on package. Bake in paper-lined 15½ X 10½ X 1" jelly roll pan. Chill or let stand several hours so tender cake may be easily handled. Invert onto a piece of heavy-duty aluminum foil, dusted with confectioners sugar; carefully remove paper from cake. Cut cake crosswise in half.
Blend mincemeat into softened ice cream. Quickly spread on one