Cook the tagliatelle in a large saucepan of boiling, salted water until al dente; usually 8-10 minutes. Drain the tagliatelle and reserve some of the cooking liquid.
Transfer back into the saucepan and dress with the olive oil, tossing well to coat evenly, adding a little of the cooking liquid to moisten the pasta as well. Heat a medium frying pan set over a moderate heat until hot and toast the walnuts for 30 seconds, tossing occasionally.
Add the pasta along with the cubed Gorgonzola. Transfer to serving plates and sprinkle the chopped parsley on top. Serve immediately.