Soak the saffron in the white wine. Add a little oil and the garlic to a frying pan, and cook until softened. Add the clams and mussels, shake the pan around, and add the white wine and saffron mixture. Bring to a boil and cook until the shellfish opens, discard any shellfish that remain closed.
Then, lay the rest of the seafood, parsley, and the cream on top. Simmer for 3 to 4 minutes and season to taste. Cook the tagliatelle in salted, boiling water until al dente. Drain and add to the fish, serve scattered with some of the leftover parsley and an extra drizzle of olive oil.