Rinse the Long-Grain White Rice under cold water until the rinse runs clear, then place it in a bowl.
Pour enough Water over the rice to completely cover it, add the Cinnamon, and let the mixture soak for at least 4 hours or overnight so the rice softens and absorbs the spice.
Transfer the soaked rice, the cinnamon, and a generous portion of the soaking liquid to a blender and blend until very smooth and milky.
Strain the blended mixture through a fine-mesh sieve or cheesecloth into a pitcher, pressing on the solids to extract as much liquid as possible.
Stir in the Whole Milk, Granulated Sugar, and Vanilla Extract until the sugar dissolves; taste and adjust the sweetness or milk ratio to your preference.
Chill the horchata for at least an hour, then serve over ice and give it a gentle stir before pouring.
