For the dough, finely grind the walnuts. Allow the butter to melt. Whip the egg whites with the sugar until stiff and fold in 2/3 of the walnuts, the melted butter and the flour.
Fill the mixture into a piping bag with a nozzle (No. 4) and pipe small heaps (2 cm ø) onto a greased, floured baking tray. Sprinkle with the remaining ground walnuts.
Bake the cookies in a heated oven at 175 °C for 10-12 minutes on the 2nd rack from the bottom. Cool the cookies, remove from the baking sheet and turn half of them to the other side.
Heat the nut nougat in a water bath until it becomes spreadable. Spread nougat on the flipped cookies and top each with a 2nd cookie.
Chop the cooking chocolate, melt in a double boiler and mix well. Make a sack out of parchment paper, fill it with the cooking chocolate and pipe fine stripes onto the cookies.
Tip: Do you prefer milk chocolate or dark chocolate? Depending on the case, use what tastes better to you.