Preheat oven to 300 degrees F. Line a large baking sheet(s) with parchment paper; set aside.

In a small bowl, combine powdered sugar and cocoa powder; set aside.

For meringue, in a medium mixing bowl, beat egg whites with an electric mixer on high speed until soft peaks form (tips curl). Gradually add granulated sugar, beating until stiff peaks form (tips stand straight). Fold in cocoa mixture. Fill a pastry bag fitted with a 1/4-inch writing (round) tip with the meringue mixture. Pipe a 1- to 11/4-inch diameter round in a spiral on prepared baking sheet; continue piping upward on outside edge to make spiral about 1 inch high. Repeat with remaining meringue mixture to make 20 to 24 cookies. Bake in preheated oven for 20 minutes. Turn off oven. Let cookies dry in the oven with the door closed for at least 1 hour.

If desired, in a small saucepan, melt the semisweet chocolate and shortening over low heat. Dip each hazelnut halfway into melted chocolate. Let excess chocolate drip off nut; set nut on a waxed-paper lined baking sheet and let stand until chocolate sets.

To serve, spoon about 1 teaspoon of chocolate-hazelnut spread into each cooled meringue. Top each with a chocolate-dipped or plain whole hazelnut.

Makes 20 to 24 servings

Make-ahead tip: Place baked meringue shells in layers separated by waxed paper in an airtight container; cover. Store at room temperature for up to 1 day or freeze for up to 1 month. Thaw shells, then fill.