With mixer, mix butter & shortening thoroughly. Add sugar gradually, continuing to beat about 5 minutes until light & fluffy. Add egg & vanilla beat well. Lightly spoon flour into measuring cup and level off. Blend flour, baking powder, salt together, add in 3 additions. Batter will be stiff.
Fill and assemble cookie gun. Use desired disc. Make cookies. Decorate with colored sugar at this stage.
Bake 10-12 minutes at 375o or until cookies just start to turn golden around edges. Be careful not to overbake. Makes about 6-7 dozen cookies