Working in two batches, pulse together the 1 ½ cups uncooked long grain white rice and 4 cups water in a large food processor or high powdered blender. Mixture does not need to be smooth.
Place the rice mixture and the 2 cinnamon sticks in a large pitcher or bowl. Cover and chill overnight.
Pour the rice mixture through a fine mesh strainer, discarding solids.
Stir in the 1 ½ cups whole milk, 12 ounces sweetened condensed milk, 2 teaspoons vanilla extract and 1 teaspoon of the ground cinnamon.
When ready to serve, fill serving glasses with ice and pour the horchata mixture over the ice. Garnish with a dusting of reserved cinnamon.
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