Beat butter and sugar until smooth and creamy. Add egg yolks, beating one at a time, until completely incorporated. Add rum extract and mix until combined.
Sift dry ingredients together and add to wet mixture. Combine well and refrigerate for at least 2 hours.
Roll out chilled dough on a floured surface to 1/8- to 1/4 inch thickness. Cut into small circles with a cookie cutter.
Place cookies on a lightly greased cookie sheet. Bake at 350 degrees for 8 minutes or until the edges are slightly golden. Remove from oven and cool completely.
Spread dulce de leche filling in the middle of one cookie and top with another cookie. Drizzle with caramel sauce or dust with powdered sugar.
This recipe is excerpted with permission from <a href="http://amzn.to/1jicfzn">"101 Gourmet Cookies for Everyone"</a> by Wendy Paul and published by Cedar Fort, Inc.