In a large saucepan, combine milk, rice, sugar, cinnamon, vanilla and raisins. Bring to a boil over medium-high heat, stirring occasionally. Reduce heat to low and cook, stirring occasionally while scraping the base and sides of the pan with a wooden spoon, until thick and creamy (about 15-20 minutes).
Once rice is soft and cooked through, add in the condensed milk and butter. Add slightly more (1/4 cup or so) of extra milk if you need to needed to achieve desired consistency.
Pour the rice among serving bowls; sprinkle with extra ground cinnamon and raisins.
Allow to cool, about 10 minutes before serving. Or, if you desire it chilled, pour pudding into a serving dish, cover, and refrigerate until chilled. Pour the rice among serving bowls, sprinkle with extra cinnamon and raisins and top with whipped cream, if desired.