Place the rice, cashews, and cinnamon stick in a bowl. Cover with water by a couple of inches and soak for at least 4 hours or overnight for best texture. See Notes for more options.
Drain and rinse the soaked cashews and rice.
Add the rice, cashews, dates, and 5 cups of water to a blender.
Blend for 1-2 minutes until smooth.
Strain the mixture through a nut milk bag into a large bowl or serving pitcher.
Add the cinnamon, vanilla, almond extract (if using), and salt. Whisk well to combine.
Serve over ice and dust lightly with ground cinnamon.
Notes
Quick soak option: Soak in very hot water and soak for 2 hours instead of 4.
No soak option: If using a high-speed blender, you can skip soaking, though soaking gives the smothest texture.
For a thinner horchata, add up to 1 extra cup of water or ¼ cup more cashews for a creamier version.
Sweetness: Start with 7-8 Medjool dates, blend, and taste. Add more for sweetness or use fewer dates for a lighter, less sweet flavor. (Deglet Noor dates may require a few extra.)
Tip: Taste after blending, this is the best time to adjust sweetness before straining.