Tender and delicious, these are the sugar cookies I've been making for twenty-something years! The dough must be chilled thoroughly, so I usually just mix it up the night before I want to do my baking. Recipe #156400 is great on these!
Cream shortening, butter, and sugar together; stir in eggs and vanilla; stir in flour, baking powder, and salt until dough (which will be very soft at this point) comes together.
Cover dough and refrigerate 6-8 hours or, preferably, overnight.
Once dough is thoroughly chilled (it will be stiff at this point) roll out about 1/6" thin on a lightly floured surface; cut cookies into desired shapes and place them onto an ungreased or parchment-lined baking sheet.
Bake at 375° for 7 minutes or just until edges of cookies begin to brown; allow cookies to cool on baking sheet for 1-2 minutes; remove cookies to cooling rack to cool completely.
NOTE: Yield will depend upon size of cookies and upon how thin you roll the dough ~ Dough rolled 1/6" thick yields 48 three-inch cookies.