Preparation

1. In a small saute pan toast the walnuts for 3 or 4 minutes on low heat. Watch closely so they don't burn.
2. In a large pot of boiling salted water, cook the pasta and drain.(Reserve 1/2 cup of the liquid if using instead of vegetable broth.) In a food processor, pulse the walnuts, parsley and the garlic clove until finely chopped. Add the grated cheese and the olive oil and process to a coarse puree. Scrape down sides and season with salt and pepper. Pulse one last time.
3. Add the vegetable broth(or reserved pasta liquid) and butter to the empty pot and bring to a simmer. Add the cooked pasta and stir often as the liquid is absorbed(about a minute or two). Add the pesto and toss until combined and all pieces are coated. Transfer to serving bowl and garnish with additional grated cheese if desired.