In a food processor, combine flour, confectioner’s sugar, nougat powder, cocoa, and margarine and process into a crumbly mixture. Add egg white and process. Dough should still be crumbly and not form a ball.

Gather up all the crumbs and press them into a ball with your hands. If the dough is too dry, add a little cold water. Wrap the dough ball in plastic wrap and refrigerate for one and a half hours.

Place dough between two sheets of Gefen Parchment Paper and roll out thin. Freeze rolled-out dough for one hour.

Preheat oven to 320 degrees Fahrenheit (160 degrees Celsius). After freezing, cut dough into 1- and- 1/2-inch (4-cm) squares, or 1- to 1- and- 1/2-inch (3- to 4-cm) circles. Place cookies on a baking sheet lined with parchment paper or a silicone baking mat.

Bake for 18 to 20 minutes until lightly browned. Let cool completely.

Heat a shallow, empty skillet. When hot, add sugar and melt until sugar turns into amber-colored caramel. Carefully add two tablespoons cream and mix thoroughly with a wooden spoon until mixture is the consistency of toffee.

At the same time, in a different pot, bring remaining 10 tablespoons cream and the milk to a boil.

Pour the boiling cream–milk mixture over the toffee mixture and cook over low heat until all the lumps disappear.

In the meantime, melt both types of chocolate.

Pour toffee mixture over melted chocolate. Blend with an immersion blender until you have a nice, smooth cream. Chill cream until it hardens slightly and is stiff enough to be piped onto cookies.

Place cream in a piping bag fitted with a star tip.Pipe cream between two or three layers of cookies to create cookie “towers.” Decorate with hazelnut shards.