Procedure:
First of all, cook the spinach, squeeze out all the liquor and put in a bowl together with the ricotta and Parmesan cheeses and a grating of nutmeg. Stir well to combine all the ingredients uniformly into a homogeneous mixture.
Then prepare the batter for the crespelle, first incorporating the eggs and salt into the flour, then adding the melted butter and the milk. Leave the mixture to stand for at least half-an-hour.
When the crepes are cooked (in practice they are thin omelettes, fried in a little butter in a small frying pan until set on both sides), spread a little of the cheese and spinach stuffing over each one and roll them up like mini Swiss Rolls.
Grease an oven dish, cover the crespelle with bèchamel sauce and dredge with plenty of Parmesan cheese.
If you like, you can even dot with a few splatters of home-made tomato sauce. Bake in a hot oven for 20 minutes.