Put the Nutella and egg in the bowl of a stand mixer or use a mixing bowl and electric whisk. Whisk for 1-2 minutes until smooth and thoroughly combined.

Next, add the sifted flour and fold it into the mixture using a spatula until the flour has fully absorbed and the cookie dough is formed.

Lay a sheet of plastic wrap on the counter and tip the cookie dough on top of it. Wrap the dough into a ball and place in the fridge for 20 minutes.

Preheat the oven to 170C (340F) and line a large baking tray with baking parchment.

Roll the cookie dough into balls weighing 20g each (if you don’t have a kitchen scale roll them into walnut-sized balls).

Using your finger or the handle of a wooden spoon, create a dent in the middle of each cookie (see photos or video for reference).

You can opt to add the filling and hazelnuts now (before baking) or do it after baking.

Bake for 10 minutes (don’t go over the time or they will dry out). Once baked, transfer to a cooling rack to cool.

Fill a piping bag fitted with a star-shaped nozzle with the Nutella. Pipe a small amount of Nutella to the middle of each cooled cookie (or do this before baking) then sprinkle over some chopped hazelnuts.