Blend 1 cup uncooked white rice with 2 cups milk and 3 cups water for 1 minute. Let mixture stand for 45 minutes - 1 hour, preferably in the refrigerator in a large, 64-ounce mason jar. Seal tightly with lid and ring.
Strain rice chunks out of the liquid by using a fine mesh strainer and funnel to transfer the liquid into a second large vessel or 64-ounce mason jar.
Add 2 more cups of milk, vanilla extract, cinnamon, and white sugar into the rice milk. Tightly seal the jar and shake.
Chill horchata for half an hour. Stir well with whisk. Serve over lots of ice!