1 c. confectioner's sugar
1 c. (2 sticks) cold unsalted butter, cut in pieces
1/2 tsp. salt
4 large egg yolks
1 tsp. vanilla extract
Egg wash (optional): 1 large egg white, beaten with 2 tsp. water
Decorating sugar and sprinkles (optional)
Place flour, sugar, butter, and salt in the bowl of a food processor; process until mixture is the texture of coarse meal. In a small bowl, lightly beat egg yolks and vanilla; with motor running, add to food processor. Process just until a dough forms. Store finished cookies in an airtight container, up to 2 weeks.