With electric mixer at high speed, cream butter and shortening until soft.
Add sugar gradually, continuing to cream, about 5 minutes until light and fluffy.
Sift flour, baking powder, salt together; add in 3 additions by hand or with electric mixer; mix well after each addition, dough will be stiff.
Shape dough into 2 rolls; wrap in plastic film, foil, or wax paper. Refrigerate at least 1 hour. ** Refrigerated dough was very difficult to extrude in manual gun. Either skip refrigeration, or let warm before using. Assemble and fill gun with cookie dough.
Extrude cookies onto an ungreased cookie sheet.
Bake 7-8 minutes at 375℉, or until just starting to turn light golden around the edges, being careful to not overbake.
Makes 6-7 dozen cookies.
