To make the sauce: First make a 'Parmigiano cream' by combining Parmigiano cheese, milk, and butter in a stainless steel bowl. Rest a bowl over a pot of simmering water. Stir until creamy and uniform and set aside. Cook the tagliolini in a pot of boiling salted water. Stir to prevent the pasta from sticking together. While the pasta is cooking (fresh pasta takes very little time to cook), place olive oil and rosewater in a saucepan over low heat. Add the chopped pistachios, ricotta and saffron. Mix thoroughly.
Drain the pasta approximately 2 minutes before the 'al dente' stage, reserving some of the pasta water. Add the pasta and the reserved pasta water to the saucepan. Mix well. Then add the Parmigiano cream, salt, to taste and stir thoroughly. Sprinkle with Parmigiano cheese and parsley. Plate and serve immediately.