Cover sheet pan with a silpat. If the silpat is too long to go into the sheet pan, flip the sheet pan over and place the silpat on top.
In the bowl of an electric mixer, using the paddle attachment, mix coconut and sugar together on low speed until well combined.
Add the butter and blend well.
Add the eggs, one at a time blending each into the coconut sugar mixture before adding the next.
Using a teaspoon and small offset spatula, place spoonfuls of batter on the silpat mat spreading each spoonful into a 2-3 inch circle. Leave at least 2 inches between cookies, as cookies will spread.
Bake cookies for 10-14 minutes, rotating every few minutes or until cookies are nice and bBrown. Remove from the oven and allow to cool for 1 minute.
Using an offset spatula, gently remove the cookie and place it, bottom side up, on a clean wax paper lined sheet pan.
Repeat spreading and baking off cookies until batter is used up.
Make the Filling
In the bowl of an electric mixer using the paddle attachment, combine the unsalted butter and the Dulce de Leche until well blended.
Add the confectioners’ sugar and mix until a light frosting forms.
Assemble the Cookies
Place approximately 1 tablespoon of the buttercream on the bottoms of half the cookies. Cover the filling with the remaining cookies so that the bottoms of each cookie face the buttercream, creating a sandwich.
Store between sheets of waxed paper in an airtight container.