In a food processor, process hazelnuts until paste-like. Add confectioners’ sugar and blend again. Melt chocolate and add to hazelnut mixture. Blend to combine. Add cookie crumbs, reserving two tablespoons, and blend again.

Pour mixture into a flat-bottomed 5×7-inch baking dish (smaller than a loaf pan). Use a spoon to flatten the top. Place in the freezer to set.

Meanwhile, prepare the coating. Melt chocolate. Once truffle filling is set, remove from freezer and spread melted chocolate over the top. Sprinkle with reserved cookie crumbs and chopped hazelnuts. Keep in freezer until very firm. Slice into squares or rectangles. Store in the freezer and serve at room temperature.