Whisk together the flour, cornstarch, salt, and baking powder in a large bowl, set aside.

Add butter and sugar to a large bowl and beat on medium speed using an electric hand mixer, for about 3 minutes or until light and fluffy.

Add the egg yolks and vanilla extract and mix until combined. Scrape the sides and bottom of the bowl down once.

Add in the dry ingredients and mix on low speed until just combined. Scrape the sides and bottom of the bowl down once.

Flatten the dough into two disks and wrap well with plastic wrap and chill for about an hour.

Preheat oven to 350 degrees F.

Let the dough stand for 10 minutes at room temperature, after that, roll it out on a lightly floured surface, between 1/4 and 1/8 an inch thickness.

Using a round cookie cutter, cut the dough and transfer to parchment-lined baking sheets. Re-roll any excess dough and repeat.

Bake cookies for about 8-10 minutes rotating the pan halfway through, the sides should be lightly golden. Allow the cookies to cool on the baking sheet before assembling.

Once cooled, add a dollop of dulce de leche onto the back of a cookie and sandwich it with the bottom of another cookie. Roll in shredded coconut and repeat with the remaining cookies.