Set oven to 350F

Spread the nuts on a baking sheet roast for about 15 minutes, stirring every 5 minutes, until the nuts are fragrant and starting to brown. Set them aside to cool on the pan.

Put the garlic and parsley in the bowl of a small food processor and pulse until both are finely minced. Add in the nuts and pulse until the nuts are well ground. There should be some variation in the size of the pieces, but you want the nuts to be well chopped. There should be a range of small walnut pieces all the way down to walnut dust (see above.) Reserve a couple of tablespoons of the nut mixture for a garnish.

Cook the pasta to just al dente. Drain and return to the pan. (Reserve a little of the cooking water)

Add in the ricotta and the Parmesan and toss well.

Add in the walnut mixture and thin the sauce with a little milk, cream, or reserved pasta water, if necessary. Bring everything up to temperature gently, and season with salt and pepper. Serve hot, garnished with the reserved nuts.