Alfajores de Dulce de Leche (Caramel Sandwich Cookies)

Paula Austin made these flaky Argentine sandwich cookies with caramel filling for her daughter-in-law's wedding brunch; they drew rave reviews. Dulce de leche, a thick, juicy caramel made with sweetened milk, is sold in Mexican markets and in some well-stocked supermarkets. If it's not available, use a thick caramel sauce or ice cream filling.
In a large mixing bowl, beat together 1 cup butter and sugar with a mixer on medium speed until smooth. Add the egg yolks, whole egg, rum and vanilla and beat until smooth.In a medium bowl, combine 2 cups flour, cornstarch, and baking powder. Add to the butter mixture, then beat until smooth. Divide the dough in half, form a disk from each half, wrap in plastic wrap and freeze until frozen, about 30 minutes.Roll out the dough. On a lightly floured surface, use a floured rolling pin to roll out one circle at a time, about 1/8 inch thick. Using a 2-to 3-inch round cookie cutter, sprinkled with flour, cut out the cookies. Arrange approximately 1 inch apart on greased 12-inch by 15-inch baking sheets. Gather the excess dough into a ball, roll out and cut out the remaining cookies.Bake in a regular or convection oven at 350 ° C until the edges of the cookies begin to brown, about 10 minutes. If you are baking two baking sheets in the same oven at once, change their position in the middle of baking. Let the cookies cool on the baking sheets for 5 minutes, then use a wide spatula to transfer them to the coasters to cool completely.Turn half of the cookies upside down and spread each one with about 1 tablespoon of dulce de leche. Top with the remaining cookies, bottom side down. Place the coconut chips in a shallow bowl. Gently squeeze each sandwich until the filling begins to ooze from the sides, then roll the edges in coconut chips.Analyze the nutritional value of each sandwich.