Preheat oven to 160C (325F). line 2 baking trays with parchment paper and set aside.

In a large bowl cream together softened butter and powdered sugar. Add egg yolks, vanilla extract, and mix until combined and smooth.

Add cornstarch, flour, salt, baking powder and mix until incorporated.

Shape the dough into a smooth disk, wrap it and Place in the refrigerator for a minimum of 1 hour.

Roll out the dough on a lightly floured surface to 1/4-inch (1/2cm) thickness. Cut out biscuits with a 2-inch (5cm) cookie cutter or a glass. Reroll leftover dough and cut more biscuits.

Place on prepared baking tray and bake for about 8-10 minutes, the cookies should stay pale on top. Allow to cool completely.

Transfer the dulce de leche into a piping bag and pipe over one cookie, gently close and create a sandwich.

For decoration roll the cookies in desiccated coconut or dust with powdered sugar.