Preheat oven to 200 C / 400 F. Grease and line a large baking sheet with baking paper.

Lay 1 sheet of puff pastry on a work surface.

Using a pizza cutter or sharp knife, cut the pastry sheet into 7 long triangles.

Spread 2 tablespoons nutella on the sheet.

Starting from the long end, roll the sheets over the filling to resemble small croissants.

Transfer the croissants to the baking tray.

Repeat with the remaining puff pastry.

Brush pastries with milk.

Bake in the preheated oven until the croissants are puffed up and golden, for about 20 to 25 minutes. 

To decorate, sprinkle the croissants with chopped hazelnuts. You can use a little nutella to act as a glue for the hazelnuts.