Beat butter, crisco and sugar together until fluffy.
Add egg and egg white.
Add vanilla.
On low, add the cake flour, cornstarch, baking powder and salt until a dough forms.
Roll 1/4 dough into a ball and place on parchment lined cookie sheet.
Sprinkle tops with a drop of flour and use a glass to press dough down into 1/2 inch thickness.
Bake 9-11 minutes at 375 degrees and then cool before frosting.