Delicious right away, EVEN BETTER the next day.
INGREDIENTS MAKES 30 SANDWICH COOKIES
1 cup unsalted butter ¾ cup icing sugar 2 tsp pure vanilla extract 3 egg yolks 1½ cups all-purpose flour 1 cup cornstarch 1 tsp baking powder 1 cup thick dulce de leche
Preheat the oven to 350° F. In a large bowl, beat together the butter and icing sugar with an electric mixer until light and fluffy, about 2 minutes. Add the vanilla and then the egg yolks, one at a time, beating well after each addition.
In a small bowl, stir together the flour, cornstarch and baking powder. Using a spatula, stir the flour mixture into the butter mixture until well combined. Roll the dough into a ball, cover in plastic wrap and refrigerate for 30 minutes to 1 hour.
Using as little flour as possible, roll out the chilled dough onto a clean surface to ¼" thickness. With a 2½" fluted cookie cutter, cut out 60 cookies. Place the cookies 1" apart on a parchment paper-lined baking sheet. Bake on the centre rack of the oven for 10 to 12 minutes, until set but still pale in colour.
Allow the cookies to cool slightly before using a metal spatula to carefully move them to a cooling rack. Let cool completely.
Spread about 2 teaspoons of the dulce de leche in the centre of the underside of 1 cookie. Sandwich with another cookie, pressing gently to spread the dulce de leche to the edges of the cookies. Repeat with remaining dulce de leche and cookies.
Dust the cookies lightly with extra icing sugar if desired; serve.