In a mini food processor, pulse the parsley with the basil and garlic until chopped. Add the walnuts, Parmesan cheese and olive oil and process to a paste. Transfer the pesto to a large bowl, stir in the ricotta and season with salt and pepper.
Cook the linguine in a large pot of boiling salted water until al dente. Drain the pasta, reserving 1/2 cup of the cooking water. Toss the pasta with the pesto and the reserved cooking water, season with salt and pepper and serve.