Rinse the Arborio rice under cold water until the water runs clear; this helps remove excess starch and prevents it from becoming gummy.
In a large saucepan, combine the rinsed rice, whole milk, coconut milk, sugar, salt, and the scraped seeds and pod of the vanilla bean. Stir to combine.
Place the saucepan over medium heat and bring the mixture to a gentle simmer, stirring occasionally.
Reduce the heat to low and cook uncovered, stirring frequently, for about 30-35 minutes, or until the rice is tender and the mixture is thickened to a creamy consistency. If using, add the raisins or dried fruit during the last 10 minutes of cooking.
Once the desired consistency is reached, remove the pot from the heat. Stir in the butter and ground cinnamon, mixing thoroughly until the butter melts completely.
Discard the vanilla bean pod. Taste the pudding and adjust sweetness if necessary.
Serve warm or chilled in individual bowls or cups. Garnish with freshly grated nutmeg.
Notes
Serve in elegant dessert bowls and top with cinnamon or whipped cream for added elegance.