Bring milk and water to a boil in a large saucepan over medium heat. Add pumpkin and salt; stir with a whisk. Reduce heat to low, and gradually whisk in polenta; cook 1 minute or until thick. Remove from heat. Add 3/4 cup grated Parmesan, cream cheese, and sage; stir until cheeses melt. Top with shaved Parmesan. Serve immediately.