Cream butter, sugar and gelatin. Add egg and vanilla. Beat well. Gradually add flour and baking powder. Blend until smooth.
Refrigerate dough until firm. (If using a cookie press, no need to refrigerate dough before use.) Roll into balls and press with bottom of glass with sugar. (Use an ungreased cookie sheet). Bake at 400 degrees F (205 degrees C) for 7-10 minutes.
