Cream the butter with the sugar until light.
Blend in the egg yolk, then the hazelnuts.
Sift the flour with the salt.
Gradually add to the nut mixture; mix well.
Pat one third of the dough out onto a sheet of waxed paper which has been lightly dusted with flour.
Cover with a second sheet of waxed paper; then roll out to 1/4 inch thickness.
Peel off the top paper, then cut with a 2-inch round cutter.
Cut out the centers of the rounds, using a thimble.
Place the rings on a greased cookie sheet, spacing them 1 inch apart.
Using a pastry tube, or a small spatula and your finger as a guide, place a ribbon of the meringue around the rings, just in the center so that a rim of dough shows on either side.
Bake in a 325° oven for 12 to 15 minutes, or until lightly browned around the edges.