Bring the water for the tagliatelle to the boil. Melt a knob of butter in a pan, then add the fresh white truffle, cut into thin slices. Once the pasta is cooked, add it to the pan with the butter and truffle and mix everything together with Stefania Calugi's Parmigiano Reggiano cream with truffle. Serve on plates, adding the thinly sliced white truffle.