Bring a large pot of salted water to a boil. Cook the rigatoni according to the package directions, or until al dente. Drain.

Meanwhile, heat 2 teaspoons of the oil in a large skillet. Add the prosciutto and cook, stirring until it begins to brown and crisp, about 5 minutes. Remove to a plate.

Heat the remaining 1 teaspoon of oil and add the onion to the skillet and cook until softened, about 2 minutes. Add the pumpkin, nutmeg, cream and chicken stock and bring to a simmer. Simmer, stirring often, until thickened, about 5 minutes. Stir in the cheese and sage. Season to taste with salt and pepper.

Add the rigatoni and half the crisped prosciutto to the skillet and toss to combine. Divide the pasta among four plates and garnish with the remaining prosciutto and Parmesan cheese. Serve.