Blend parsley, walnuts, 3 garlic cloves, thyme leaves, and chopped rosemary in food processor until finely chopped. Add 3 tablespoons oil, and blend until smooth. Set aside.

Cook kale in large pot of boiling water 5 minutes, or until tender. Remove kale with large sieve, and drain. Add pasta, remaining garlic cloves, thyme, and rosemary sprigs to boiling water, and cook according to package directions until al dente. Reserve 1 cup pasta cooking water, then drain pasta.

Meanwhile, heat remaining 1 tablespoon oil in large pot or Dutch oven over medium-high heat. Add mushrooms and onion, and saute 12 minutes, or until tender and golden. Add pesto, and saute 2 minutes, or until sauce begins to stick to bottom of pan and turns golden brown. Add vegetable broth, and simmer 2 minutes, or until liquid is reduced by half, scraping sauce from bottom of pan.

Add kale and pasta to mushroom mixture, and toss to coat. Stir in reserved pasta cooking water to moisten, if desired. Add Parmesan, if using, and season to taste with black pepper.