1 cup cornstarch
3/4 cup all-purpose flour, plus more as needed
1 teaspoon baking powder
1/2 teaspoon baking soda
1/4 teaspoon fine salt
8 tablespoons unsalted butter (1 stick), at room temperature
1/3 cup granulated sugar
2 large egg yolks
1 tablespoon pisco or brandy
1/2 teaspoon vanilla extract
1 cup Dulce de Leche, at room temperature (you can do premade, or make your own)
Powdered sugar, for dusting
Place the cornstarch, measured flour, baking powder, baking soda, and salt in a medium bowl and whisk briefly to combine; set aside. In another bowl, (you can use a hand mixer if you like) cream together the butter and sugar until the mixture is light & fluffy. Add the egg yolks, brandy, and vanilla and mix until incorporated. Gradually add the reserved flour mixture and mix until just incorporated.
Turn the dough out onto a piece of plastic wrap, shape it into a smooth disk, and wrap it tightly. Place in the refrigerator until firm, at least 1 hour.
Meanwhile, heat the oven to 350°F and arrange a rack in the middle. Line 2 baking sheets with parchment paper and set aside.
Remove the dough from the refrigerator, unwrap it, and place it on a lightly floured work surface. Lightly flour the top of the dough. Roll to 1/4-inch thickness (the dough will crack but can be easily patched back together). Stamp out 24 rounds using a plain or fluted 2-inch round cutter, re-rolling the dough as necessary until all of it is gone.
Place the cookies on the prepared baking sheets, 12 per sheet and at least 1/2 inch apart. Bake 1 sheet at a time until the cookies are firm and pale golden on the bottom, about 12 to 14 minutes. (The cookies will remain pale on top.) Transfer to a wire rack to cool completely.
Flip half of the cookies upside down and gently spread about 2 teaspoons of the dulce de leche on each. Place a second cookie on top and gently press to create a sandwich. Dust generously with powdered sugar before serving.
Recipe adapted from CHOW.com.