Preheat oven to 375F. Lightly grease a cookie sheet; set aside. Beat butter in a large mixing bowl with an electric mixer on medium to high speed for 30 seconds. Add brown sugar, baking powder, and salt. Beat until combined, scraping side of bowl occasionally. Beat in eggs and cocoa powder. Beat in as much flour as you can with the mixer. Stir in any remaining flour, the hazelnuts, and 4 ounces bittersweet chocolate with a wooden spoon.

Divide dough in half. Shape each portion into a 9-inch-long roll. Place rolls 4 inches apart on prepared cookie sheet; slightly flatten each roll to 2 inches wide.

Bake in preheated oven for 20 to 25 minutes or until a wooden pick inserted near centers comes out clean. Cool on cookie sheet for 45 minutes. Reduce oven temperature to 325F.

Cut each roll diagonally into 1/2-inch-thick slices, slicing carefully with a serrated knife. Place slices, cut sides down, on cookie sheet.

Bake in 325F oven for 8 minutes. Carefully turn slices over and bake for 7 to 9 minutes more or until dry and crisp. Transfer to wire racks and let cool, about 1 hour.

Microwave chopped chocolate and shortening in a small microwave-safe bowl on 50 percent power (medium) for 1 to 2 minutes or until melted, stirring twice. Dip one end of each cookie into melted chocolate; let excess drip back into bowl. Place cookies on waxed paper; let stand until set. Makes 2 dozen cookies.

To toast nuts, spread them in a single layer in a shallow baking pan. Bake in a preheated 375F oven for 4 to 5 minutes or until nuts are slightly golden brown, stirring once or twice. Wrap warm nuts in a clean kitchen towel. Rub nuts in towel to remove any loose skins; cool completely. Chop nuts and set aside.

Place cookies in layers separated by pieces of waxed paper in an airtight container; cover. Store at room temperature for up to 3 days or freeze for up to 3 months. Thaw cookies, if frozen, before serving.