Step 1In a food processor, cream the butter. Scrape down the sides of the bowl. While the machine is running, mix in the granulated sugar, powdered sugar, almond meal and salt just until incorporated.
Step 2Add the egg, beating continuously. Add the flour and pulse just until the dough pulls away from the sides. Form the dough into a ball, cover in plastic wrap and refrigerate for at least 3 hours, or overnight.