Cook the pasta. Cook the pasta in a large pot of boiling, salted water until it's al dente. (Al dente means "to the tooth." The pasta should be tender, but with a bite to it.) Drain the pasta and save about ¼ cup of the water. Then toss it with a bit of olive oil, cover and set aside.
Cook the sausage. Add the sausage to a large sauté pan. Break up the pieces with a wooden spatula and sauté just until cooked through, about 7 minutes. (If there isn't enough grease from the sausage, add a bit of olive oil.) Add the cooked sausage to a bowl and set aside.
Sauté onions and garlic. Add the onions and garlic to the same pan over medium-low heat, adding a drizzle of oil if they begin to stick. Sauté, mixing often, until the onions are soft and beginning to brown, about 10 minutes.
Add sausage, sage and spices. Return the cooked sausage to the pan and add the sage, cinnamon and chili paste. Mix and sauté for another few minutes to blend the flavors.
Deglaze the pan and add remaining ingredients. Turn the heat to high and add the sherry. Use a flat-edged spatula to scrape the bottom of the pan -- to bring anything that's stuck back into the mixture.Add the reserved pasta water, chicken stock and pumpkin and stir until blended. Turn the heat to low, simmer for 5 minutes and then season to taste with salt and pepper.
Combine the sauce with the pasta. Add the cooked pasta to the pan and gently mix until it's well coated with all of the ingredients. Let this cook on low heat just to be sure the pasta is hot, about 4 minutes.