In a large bowl, sift together the flour, cornstarch, baking powder, baking soda and kosher salt. Set aside
1 cup all-purpose flour, 1 cup cornstarch, 1 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon kosher salt
In the bowl of an electric mixer, beat sugar and butter until light and fluffy, about 3 minutes. Add yolks and beat to combine. Then the vanilla extract, water and lemon zest beat until just combined.
½ cup granulated sugar, 8 tablespoons unsalted butter (1 stick), 2 large egg yolks, 1 teaspoons vanilla extract, 2 teaspoon finely grated lemon zest, 2 tablespoons warm water
Add flour mixture, and mix on low speed until the dough just comes together.
Wrap the dough in plastic and chill until firm, at least 2 hours.
Heat oven 350 degrees. Line baking sheets with parchment paper.
Remove dough from plastic wrap and place on a lightly floured surface, flour a rolling pin and roll out to about ¼ inch thick. Cut the dough with a 2 inch cookie cutter.
Place cookies on prepared sheet pans about about 1 inch apart.
Bake for about 9 minutes or until firm and edges are pale golden and the middle of the cookie is firm.
Transfer baking pan to a rack and allow to cool completely before removing from baking sheet.
Spread 1 tablespoon of dulce de leche onto the back of half the cookies. Place a second cookie on top and gently press to create a sandwich and repeat.
8 ounces Dulce De Leche, 1 cup coconut flakes
Roll sides in coconut and dust generously with powdered sugar if you like before serving.
powder sugar