Butter Cookies with Dulce de Leche
3/4 stick (6 tablespoons) unsalted butter, softened
1/3 cup cornstarch
3/4 to 1 cup all-purpose flour
1/4 teaspoon baking powder
1/8 teaspoon salt
1/4 cup granulated sugar
2 large egg yolks
1 tablespoon Pisco or regular brandy
1/4 teaspoon vanilla
About 1/4 cup dulce de leche*
Confectioners sugar for dusting
Put oven rack in middle position and preheat oven to 350°F. Butter a large baking sheet.
Whisk together cornstarch, 3/4 cup flour, baking powder, and salt in a small bowl.
Beat together butter and sugar in a large bowl with an electric mixer until light and fluffy, then beat in egg yolks, Pisco, and vanilla. Stir in flour mixture until combined, adding 1 to 2 tablespoons flour if dough is sticky. (Dough should be soft.)
Form dough into a disk and roll out into an 11-inch round (1/8 inch thick) on a lightly floured surface with a lightly floured rolling pin. Cut out 32 rounds with cutter (reroll scraps if necessary) and transfer to sheet, arranging rounds 1/2 inch apart.
Bake until firm and pale golden around edges, 12 to 15 minutes. Transfer to a rack and cool 10 minutes.
Sandwich cookies with about 1/2 teaspoon dulce de leche. Dust with confectioners sugar