In a large saucepan, combine rice and 5 cups milk; bring to a boil. Reduce heat to medium; simmer, stirring occasionally, until rice is tender, 15 to 17 minutes.
Meanwhile, in a medium bowl, whisk together sugar, eggs, vanilla, cardamom, and remaining cup milk. Slowly pour egg mixture into rice mixture; cook over medium-low, stirring constantly, until pudding coats the back of a spoon, 3 to 5 minutes.
Remove from heat; stir in raisins. Pour pudding into a 6-quart casserole dish or large bowl; let cool to room temperature. Cover and refrigerate at least 1 hour (or up to 3 days). Serve pudding garnished with more raisins and cardamom.
Pudding Pizzazz: Tweak the flavor by trading ingredients. Try pistachios or chopped dried apricots instead of raisins, or use ground nutmeg instead of cardamom or cinnamon.