Combine cornstarch, powdered sugar, and flour in the bowl of a stand mixer, or large bowl. Add in the room temperature butter, and combine until it comes together into a dough. Add in the vanilla paste, and mix through the dough.

If dough is too soft to handle, wrap in plastic wrap and refrigerate for 30 minutes. Roll out the shortbread cookie dough on a lightly floured surface to ¼ inch thick, and cut into shapes with cookie cutters. Or form 1 inch balls and flatten with a fork.

Bake at 300 F, on an ungreased cookie sheet, for 15-20 minutes until just beginning to brown on the edges. Cool cookies on a wire rack. Store in an airtight container.