Rinse the rice under cold water until the water runs clear.

In a bowl, combine the rinsed rice, almonds, cinnamon stick, and 4 cups of water.

Soak the mixture for at least 3 hours, or overnight for best results.

After soaking, discard the cinnamon stick and drain the rice and almonds.

In a blender, combine the soaked rice and almonds with 2 cups of fresh water. Blend until smooth.

Strain the mixture through a fine mesh sieve or cheesecloth into a large bowl, discarding the solids.

Add the remaining 2 cups of milk, sugar, and vanilla extract to the strained liquid. Stir well.

Chill the horchata in the refrigerator for at least 1 hour.

Serve over ice, garnished with ground cinnamon.

Enjoy your refreshing horchata!