Make the pesto: Bring 5 quarts water to boil in large pot. Once boiling, add a large pinch of salt. Blanche kale in boiling water for about 3 minutes. Pull kale from water and let cool, reserving water for cooking pasta.
Combine all ingredients in a blender and process until a smooth paste has formed. If pesto is too dry, slowly add more olive oil. (If making ahead, pesto can be stored in refrigerator for up to 4 days. Top pesto with olive oil before sealing to prevent browning.)
Make the pasta: Add 1 tablespoon salt to reserved kale water and return to boil. Add pasta to pot and stir. Cook until al dente. Reserve ½ cup pasta water, then drain pasta.
Transfer pasta to a large mixing bowl. Add pesto and 2 tablespoons pasta cooking water and toss pasta gently to evenly cover with pesto. If it looks dry, add more cooking water a tablespoon at a time.
Serve pasta garnish with roasted walnuts, fresh ricotta, and a drizzle of olive oil.