Peruvian Alfajores with Dulce de Leche

Preheat oven to 300°F. Add butter, flour, corn starch, powdered sugar, and salt to the bowl of an electric mixer. Using the paddle attachment, mix the flours and butter until the mixture resembles coarse sand. Press and knead the dough by hand until a smooth dough forms. The mixture should come together when pressed together. If the dough seems dry or crumbly, wet your hands with warm water and continue kneading. Once you’ve achieved a smooth dough, wrap in plastic and place in the fridge to chill for at least 30 minutes. Once chilled, roll the dough out to a thickness of between 1/8-1/4 inch. Cut out the cookies and bake at 300°F for 12 minutes. Allow the cookies to cool completely before filling with Dulce de leche and dusting with powdered sugar.