For the Mold:
Remove the green part of the leeks. Wash the leeks well, slice them thin and cook them in boiling water for 20 mins. Combine ricotta, whole eggs, Parmigiano and the nutmeg in a skillet. Drain the leeks, let them cool and add them to the rest. Mix well and add salt, then blend in a food processor, dripping in the olive oil until you get a smooth mixture.
Pour into a baking tray, bake for 20 mins. at 400ºF, and then cover the try with aluminum foil so as not to let the top of the mold go brown, and bake for another 20 mins. Check baking with a toothpick.
Sformato can be made in a big round mold or in a number of small pudding molds.
For the Sauce:
In the meantime, slowly fry the chopped onion in oil; when brown add in thinly sliced potatoes, a ladleful of broth and salt.
Cook for 10 mins. Add the saffron diluted in a little boiling hot vegetable stock, mix and continue cooking until the potatoes are quite tender and little mushy.
Mash the potatoes with a ricer or a sieve, and then put them back on the fire. If the sauce is too thick, dilute it with a little milk or cream an a very hot fire (do not boil). Stop cooking when the sauce has reached desired thickness. Turn the mold upside down into a platter and serve dipped in warm sauce.
