Preheat your oven to 170 degrees C (338 ℉). You may use an electric mixer/beaters or mix by hand.
Cream butter and sugar till it is light and fluffy occasionally scraping down the sides of the bowl with a spatula.
Add the egg yolks and mix until well combined, then mix your dry ingredients in a separate bowl.
Gradually add your mix of dry ingredients to your butter and egg mixture mixing until well combined. You should have dough like mixture to form your cookies.
Turn the dough out and divide into two, then shape each portion into a long cylinder or a log. Each portion of dough should be about 450g each (about 16 ounces). Wrap each log in plastic wrap and refrigerate for at least an hour until firm. Each log should be roughly 25 cm (10 inches) in length and 5 cm (2 inches) in diameter.
Once your dough is nice and firm, place on a cutting board and with a sharp knife cut your dough out into medallions. Each cookie should be no more than 15mm ( 1/10th inch) in thickness; you will get roughly 15 cookies per log of dough. As this cookie is a sandwich be sure that you have an even amount of cookies to bake.
Place the cookies out onto a tray with baking paper being sure to leave at least 1 cm (1/3 inch) space between, place into the oven and cook for roughly 12-14 minutes. Your cookies should be firm and lightly golden on the bottom and still pale on the top. Allow the cookies to cool out of the oven, you won’t need to use a cooling rack.
Once your cookies are completely cooled take one cookie and place a tablespoon of dulce de leche (see recipe below) onto the base of the cookie and smooth until evenly covered. Then place another cookie on top to sandwich between the dulce de leche
The finish your cookies roll them through some desiccated coconut so it sticks to the dulce de leche and lightly dust with icing sugar.