Chef John's Horchata

Place rice almonds cinnamon stick and sugar in a blender. Pour in about 4 cups of the water. Pulse on and off to start. Then blend on high speed until ingredients have been chopped up into very small pieces about 30 seconds. Add the remaining 3 cups cold fresh water. Let mixture sit at room temperature about 4 hours. (Or you can refrigerate it overnight.) Stir occasionally.

Strain through several layers of cheesecloth into a pitcher. Refrigerate until chilled about 2 hours. Serve topped with a dusting of cinnamon.