Rinse the rice under cold water until the water runs clear. Drain and set aside.
In a medium saucepan, combine the rinsed rice, milk, heavy cream, sugar, salt, and cinnamon stick. Stir to dissolve the sugar.
Bring the mixture to a gentle boil over medium heat, stirring frequently to prevent sticking.
Reduce the heat to low and simmer uncovered, stirring occasionally, for about 50–60 minutes, or until the rice is tender and the mixture has thickened to a creamy consistency.
Remove the saucepan from the heat. Discard the cinnamon stick and stir in the vanilla extract and butter until fully incorporated.
Let the pudding cool slightly, then serve warm or chilled, garnished with raisins or slivered almonds if desired.
Notes
Serve warm or chilled, optionally garnished with raisins or slivered almonds.