Note: have some cooking oil on hand in case your dough is dry - the texture of the Nutella can be different towards the top or bottom of the jar, and depending on how old your Nutella is. Hazelnut oil would be ideal.
Preheat oven to 350 degrees F
Line two cookie sheets with parchment paper or silicone baking mats. Set aside.
In a large mixing bowl, combine the flour, Nutella and egg.
Portion the dough into 2 Tablespoon sized balls.
If the dough crumbles and doesn't roll into a ball easily, knead some cooking oil into the dough.
Flatten the cookie balls with the bottom of a glass.
If you want to shape the cookies, do it now and remove excess dough.
Place the flattened cookies onto the prepared cookie sheets.
Bake for 8-10 minutes, until set.