Cook the tagliatelle in boiling salted water according to package directions until al dente.
Meanwhile rinse and shake dry the parsley and pluck the leaves from the stems. Toast the pine nuts in a dry pan. Peel and coarsely chop the garlic.
Combine the pine nuts, parsley leaves, garlic and olive oil and purée. If necessary, add some oil. Season with salt and pepper. Finely grate the parmesan and stir in.
Arrange the tagliatelle on a plate and serve with the pesto.