Heat the horchata, reserving a little to dissolve the pudding mix packet.

Once the horchata is hot, add the dissolved pudding mix and stir constantly until it comes back to a boil (follow the packet instructions as if using milk).

Pour into a dish, jars, or directly into serving glasses. Let cool, then refrigerate for about four hours, until set.

When ready to serve, sprinkle with ground cinnamon and add some wafer cookies on the side.