1. Remove the parsley stems, rinse, dry and chop finely. Chop the walnuts and mix, in a bowl, with parsley, marjoram, oregano, ricotta and grated pecorino.2. Vigorously mix the mixture with a wooden spoon until it becomes frothy and smooth.3. Cook the tagliatelles in a pot of boiling salted water.4. Just before draining the pasta, reserve 4 c.à.soupe of the cooking water and dilute it in the ricotta mixture. Season with salt and pepper, and mix again. Drain the tagliatelles al dente, and put them in a bowl with the ricotta mixture, mix well and serve immediately.