Place the center cutouts 1 inch apart on a separate ungreased cookie sheet. Bake in the 300 degree F oven for 12 to 14 minutes or until tops are very lightly browned. Transfer cookies to a wire rack; let cool. Spread about 1/4 teaspoon desired flavor jam or marmalade on the flat side of half the cookies. Top with remaining cookies, flat sides down. Sprinkle cookies with powdered sugar before serving.
*To toast hazelnuts (filberts):
Spread hazelnuts (filberts) in a single layer in a shallow baking pan. Bake in a 350 degree F oven for 10 to 15 minutes or until light golden brown, watching carefully and stirring once or twice so the nuts don't burn. Cool slightly. Place the nuts on a clean kitchen towel, fold towel over top, and rub vigorously to remove the skins.
If you don't have a donut cutter, make cutouts using a 2-1/2-inch round cutter. Then use a 1-inch round cutter to make cutouts in the centers of the 2-1/2-inch dough circles.
Layer Nut Rings or Duce Cookies between sheets of waxed paper in an airtight container; cover. Store Nut Rings at room temperature for up to 3 days or freeze for up to 3 months. Store Duce Cookies in the refrigerator for up to 1 day or freeze for up to 3 months.