Preheat oven to 375 degrees F (190 degrees C). Line a baking sheet with parchment paper.
Roll out 1 puff pastry sheet and place on the prepared baking sheet.
Spread chocolate-hazelnut spread evenly onto puff pastry with the back of a spoon. Roll out the second sheet of puff pastry and place on top.
Place a glass or Mason jar face-down in the center of the puff pastry. Cut pastry into 4 equal strips with a sharp knife, stopping at the border of the glass. Cut through each quarter again, making 8 strips, and again, ending up with a total of 16 equal parts, while keeping the center intact. Twist 2 parts away from each other; pull outward and seal seams together. Repeat with the rest of the parts until pastry resembles a star.
Brush top with beaten egg.
Bake in the preheated oven until puffy and golden brown, 25 to 30 minutes. Cool slightly, about 5 minutes, before serving.