In a large bowl, combine the rinsed rice and water. Let it soak for at least 4 hours or overnight.

After soaking, drain the rice and transfer it to a blender. Add 4 cups of fresh water and blend until smooth.

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

To the strained rice water, add milk, sugar, vanilla extract, ground cinnamon, and a pinch of salt. Stir well to combine.

Refrigerate the horchata for at least 1 hour before serving. Serve over ice and sprinkle with additional cinnamon if desired.