Thấy các quán giải khát Mễ hay có loại thức uống màu trắng như sữa khá ngon, tìm trên Net thì "công thức" làm ra món này như sau:
1 1/4 cups long-grain white rice
2 (1/2-inch) cinnamon sticks
1 cup blanched, sliced almonds, toasted and cooled
4 cups water
1/2 cup granulated sugar
1 (2-inch-long) lime zest strip, removed with a vegetable peeler
1 tablespoon freshly squeezed lime juice
Pulverize the rice and cinnamon in a spice grinder in batches until the mixture resembles a fine powder. Place in a 2-quart container with a tightfitting lid. Next, pulverize the almonds in the spice grinder until finely ground but not a paste. Add the almond powder to the rice-cinnamon mixture, pour in the water, and stir to combine. Cover and let sit at room temperature for 12 hours.
Add the sugar and zest to the mixture and, using a blender, blend in batches on high until smooth. Pour the mixture through a fine-mesh strainer placed over a bowl. Using a rubber spatula, press on the solids to extract all of the liquid, then discard the solids.
Stir the lime juice into the horchata, then transfer the beverage to a pitcher and chill in the refrigerator. Serve over ice.