n a large saucepan, bring rice, sugar, salt, and 4 1/2 cups milk to a boil over medium-high. Reduce heat, cover, and simmer 25 minutes. Uncover and cook, stirring constantly, until rice is tender and pudding is creamy, 5 minutes. Stir in vanilla and remaining 1/4 cup milk.
Transfer to a serving dish and press plastic wrap directly on surface to prevent a skin from forming. Refrigerate until chilled, at least 1 hour (or up to 3 days). To serve, stir in heavy cream and sprinkle with cinnamon.