Cut the Stelvio cheese into half-inch cubes and place them in a bowl with milk for 2 hours. Heat up the milk, butter and Stelvio cheese in a bain-marie boiler over low heat until the mass begins to string together; once the cheese has melted, mix it with egg yolks, then turn up the heat until the water boils. At first the mass of milk and cheese will become more and more liquid, then rising in temperature it will begin to thicken and when the mass will veil the ladle remove the bowl from the water and pour the mixture in a basin. Once cooled, form small balls with a diameter of 1.5 cm. Boil, peel and mash the potatoes, add salt, 1 egg, the spinach puree and the flour then roll out the mixture with a rolling pin to reach a thickness of 4 mm which is the thickness of 2 Euro coins one on top of the other, form circles with a diameter of 8 cm, brush them with whisked egg, put the ball of fondue in the center and close them. Boil the gnocchi in salted water for 5-6 minutes, take them out of the water with a perforated ladle, place them on a plate, sprinkle them with Parmigiano Reggiano, drizzle with good melted butter and cut the truffle very thin with a truffle-cutter.