Steps

In a container put the flour, salt, eggs and at last the milk.
Mix all with an hand blender for around 1 min.
This will ensure you will not have any lumps.
If you want to have no doubt about that, simply pass the mix through to a sieve.

Put a large flat no sticky pan on a very slow fire.
Grease the pan with some butter and when it start to simmer add one ladleful of mix in the centre of the pan and gently spread it all on the surface.
Let it cook at really slow heat and around 1 min flip it on the other side to complete the cooking.
Take off from the pan and put a full spoon of nutella in the centre and fold it in 4.
Now, gently press with a spatula to spread evenly the nutella on all the internal surface.
To serve warm.