Sonia's Dulce de Leche Cookies

Directions

1. Beat butter with sugar for 3 minutes or until light and fluffy. Beat in egg yolks and vanilla, scraping bowl as needed. Stir cornstarch with flour, baking powder, baking soda and salt in a separate bowl. On low speed, gradually add cornstarch mixture to butter mixture, just until uniformly incorporated. Form dough into a disc; wrap tightly in plastic wrap and chill for at least 1 hour or until firm.
2. Preheat oven to 350°F. Line baking sheets with parchment paper. Working on a lightly floured surface, roll dough to about 1/8-inch thick (if dough cracks, it patches easily). Use a 2-inch round cookie cutter to cut 36 rounds and place on prepared baking sheets.
3. Bake, in batches, for 8 to 9 minutes or until just pale golden on bottom. (Do not overbake.) Transfer to a wire rack to cool completely.
4. Spread bottom of one cookie with 1 1/2 tsp Dulce de Leche spread; sandwich with a second cookie. Dust both sides of cookies with icing sugar.
5. Tip: If a thick Dulce de Leche is hard to find, use this shortcut recipe: pour 1 can (300 mL) Dulce de Leche flavoured condensed milk into a small heavy pot set over medium heat. Bring to a boil. Boil, stirring constantly, for 4 minutes or until thickened. Cool to room temperature before using.
6. Tip: Make several batches of these cookies; wrap them up in cute boxes and offer them as holiday gifts.