Preheat your oven to 325°F (165°C).
Cook the rice according to the package instructions. Once cooked, set it aside to cool slightly.
In a large mixing bowl, whisk together the milk, heavy cream, granulated sugar, and salt until the sugar is dissolved.
In a separate bowl, lightly beat the eggs. Slowly add the beaten eggs to the milk mixture, whisking constantly to combine. Add the vanilla extract and ground cinnamon, and mix well.
Stir the cooked rice into the custard mixture. If using raisins, fold them in at this stage.
Pour the mixture into a greased 2-quart baking dish. Dot the top with small pieces of butter.
Cover the baking dish with aluminum foil and bake in the preheated oven for 45 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the pudding is set and the top is lightly golden.
Allow the rice pudding to cool slightly before serving. It can be enjoyed warm or chilled, depending on your preference.