Grind the rice in a spice grinder or blender until it is the consistency of coarse meal.
Pulverize the almonds.
Pour into a pitcher with the warm water. If using stick cinnamon,
add it now.
When the water has chilled to room temperature, cover and place in the refrigerator for at least 6 hours, or up to overnight.
Blend the rice/ water/ almond mixture in batches until smooth. (NOTE: if using stick cinnamon, discard the cinnamon before blending).
Strain the blended rice mixture through a fine mesh strainer lined with cheesecloth. Squeeze solids to release all the liquid. Re-blend the rice solids once more, and strain again to get as much rice-y goodness as possible.
Add milk, coconut milk, sugar, cinnamon, and vanilla. Stir until sugar dissolves. Taste for sweetness, and add more sugar to taste if necessary.
Server over ice, garnish with stick of cinnamon and a dusting of ground cinnamon.