Oatchata or oat horchata is a delicious way to make horchata using oats.
Soak the oats and cinnamon stick in 6 cups of water for a couple of hours.
Transfer the oats, cinnamon stick, and water to a blender and blend for 1-2 min. Do this in two batches if your blender is too small.
Strain into a pitcher using a fine mesh strainer and discard the solids.
Add the sugar, vanilla, evaporated milk and two cups of water to the blender and blend until smooth. Strain into the pitcher. Add two more cups of water to the pitcher and stir.
Serve over ice. Refrigerate any leftover.