1In a medium bowl, cream butter using an electric mixer set at medium speed. Add confectioners and brown sugars and beat until smooth. Add egg yolks and vanilla, and mix at medium speed until light and fluffy. Scrape bowl. Add the flour and blend at low speed until thoroughly combined.
2Gather dough into a ball and flatten to a disk. Wrap dough tightly in plastic wrap or place in plastic bag. Refrigerate for 1 hour.
3Prepare the filling; scald the cream in a small saucepan over medium heat. Add the chocolate chips and stir until melted. Remove from the heat. Preheat oven to 325F.
4Using a floured rolling pin, roll dough on floured board to 1/4-inch thickness. Cut circles with a 2-inch-diameter cookie cutter and place on ungreased cookie sheets, 1 inch apart. Contiue using dough scraps, rerolling and cutting until all dough is used. Drop 1 tsp. of chocolate filling in center of each circle and top with another circle. Completely seal the edges using a fork. Bake 15 to 16 minutes, or until cookies are golden brown. Transfer cookies to a cool, flat surface with a metal spatula. Sprinkle with a dusting of confectioner sugar.