Rinse the Long-Grain White Rice under cold water until the rinse runs clear to remove excess starch.
Combine the rinsed rice, Water, a Cinnamon Stick, and a small pinch of Salt in a medium saucepan. Bring to a gentle boil over medium heat, then reduce to a low simmer and cook uncovered until most of the water is absorbed and the rice is just tender, about 10–15 minutes.
Lower the heat and stir in the Whole Milk. Continue to simmer very gently, stirring frequently to prevent sticking, until the rice is creamy and tender, about 20–30 minutes (add a splash more milk if the mixture becomes too dry).
Stir in the Sweetened Condensed Milk and cook for another 3–5 minutes so the sweetness and creaminess blend through the pudding.
Remove the pan from the heat and stir in the Vanilla Extract. If using, fold in the Raisins so they plump slightly in the warm pudding.
Discard the Cinnamon Stick, spoon the Arroz con Leche into serving bowls, and sprinkle each portion with a little Ground Cinnamon. Serve warm or chilled according to your preference.
