1 can of Goody Sweetened Condensed Milk
½ cup blanched hazelnuts
1 cup all-purpose flour, plus more for dusting
¾ cup cornstarch
1 tsp baking powder
½ tsp baking soda
¼ tsp salt
1 stick unsalted butter, at room temperature
1/3 cup granulated sugar
2 large egg yolks
1/2 tsp pure vanilla extract
Confectioners' sugar, for dusting
1.First caramelize the condensed milk. Remove the paper off the condensed milk tin. In a saucepan, add some water, then place the tin and leave for 2 hours and 30 minutes on low heat and add water when needed. Remove from heat and leave to cool down before opening
2.Preheat the oven to 180 degrees C.
3.In a food processor, finely grind the hazelnuts, then spread on a baking sheet; bake for 12 minutes until golden.
4.Whisk the flour, cornstarch, 1/3 cup of the ground hazelnuts, the baking powder, baking soda and salt in a bowl; set aside. Beat the butter and granulated sugar in a large bowl with a mixer on medium-high speed for about 3 minutes until light and fluffy. Add the egg yolks and vanilla; beat until incorporated. Reduce the mixer speed to low; add the flour mixture and beat until just combined. Turn onto a sheet of plastic wrap; shape into a disk. Wrap and refrigerate until firm, at least 1 hour.
5.Position racks in the upper and lower thirds of the oven. Line 2 baking sheets with parchment paper. Dust the dough with flour and roll out into a 15-by-30-cm rectangle (1/2 centimeter thick) on a floured surface. Cut into 2 centimeters squares; arrange 1/2 1 cm apart on the baking sheets. Cut out heart shape from the middle of half of the squares using a small cutter. Refrigerate until firm, 15 minutes.
6.Bake for 12 to 14 minutes, switching the pans halfway through, until the cookies are golden on the bottom. Let cool 5 minutes, then transfer to racks to cool completely. Stir together the dulce de leche and the remaining ground hazelnuts. Sandwich between the plain and cutout cookies. Dust with confectioners' sugar. Serve