On a baking sheet covered with parchment paper, roast the ground hazelnuts in the oven at 300°F (150°C) for 10 minutes. Sieve together the confectioners sugar and the roasted ground hazelnuts. Beat the egg whites, adding the superfine sugar in three batches, until you get a soft meringue. By hand, add the sieved mixture, gently lifting and turning the preparation with a spatula. Lay a baking frame on a tray covered with a sheet of parchment paper, and spread the preparation evenly using an angled offset spatula; sprinkle the crushed hazelnuts evenly over the top. Bake in a convection oven at 340°F (170°C) for approximately 30 minutes, quickly opening and closing the oven door once to prevent the dacquoise from rising and falling due to the concentration of steam in the oven.