How to Make It
Preheat the oven to 350°. Toast the walnuts in a pie plate for 7 minutes, or until golden; let cool. Coarsely chop 1/4 cup of walnuts and transfer to a bowl; add the 2 tablespoons of chopped parsley and half of the grated Parmesan.
In a large pot of boiling salted water, cook the pasta until al dente; drain. In a mini food processor, pulse the remaining 1/2 cup of walnuts with the 1/4 cup of parsley leaves and the garlic until finely chopped. Add the remaining grated Parmesan cheese and the olive oil and process to a coarse puree. Season the pesto with salt and pepper.
Return the pasta to the pot. Add the vegetable stock and butter and simmer until the liquid is nearly absorbed, 1 to 2 minutes. Off the heat, add the pesto and toss until combined. Transfer the pasta to a bowl, garnish with the walnut, parsley and Parmesan topping and Parmesan shavings and serve.