Lightly grease a cookie sheet and set aside. Beat the 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 sides of bowl occasionally. Beat in the 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 the dough in half. Shape each portion into a 9" long roll. Place rolls 4 inches apart on the prepared cookie sheet; slightly flatten each roll to 2 inches wide.
Bake in preheated oven for 20-25 minutes or until a wooden pick inserted near center comes out clean. Cool on cookie sheet for about 45 minutes. Reduce oven temperature to 325*F.
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 325*F oven for 8 minutes. Carefully turn slices over and bake for 7-9 more minutes or until dry and crisp. Move to wire racks and let cool, about 1 hour.
Makes 2 dozen.
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(or you can melt in a small saucepan on the stovetop, just stir and watch carefully). Dip one end of each cookie into melted chocolate; let excess drip back into bowl. Place cookies on waxed paper; let sit until set.
*Note: To toast nuts, spread them in a single layer in a shallow baking pan. Bake in a preheated 375*F oven for 4-5 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.
To Store: 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.