Combine cream, 3/4 cup milk and salt in a medium saucepan and heat over medium heat until steaming. Whisk the remaining 1/4 cup milk and cornstarch in a small bowl until smooth. Whisk the cornstarch mixture into the cream mixture and cook, whisking, until slightly thickened, 2 to 3 minutes. Remove from heat. Add 1 3/4 cups Parmesan and stir until melted.