In a Dutch oven, cook sausage, mushrooms and onion over medium-high heat until sausage is no longer pink and vegetables are tender, 8-10 minutes, breaking up sausage into crumbles; drain. Add garlic; cook 1 minute longer. Add stock, pumpkin, sugar and seasonings. Bring to a boil; reduce heat. Cover and simmer 10 minutes., Stir in cream. In a small bowl, mix water and cornstarch until smooth. Stir into pan. Bring to a boil; cook and stir until thickened, 1-2 minutes. Add cheese; cook and stir until melted.