Combine the rice and melon seeds (if using) in the jar of a blender, and whizz a couple of times until the mixture is coarsely ground.

Transfer to a large bowl, add the hot water and the cinnamon stick (broken roughly into pieces), and allow this to sit covered for about 5-6 hours or overnight.

Note that if you live in a very hot region, you might want to have the soaking happen in a refrigerator! Colder clime-dwellers can leave the bowl on a counter-top, covered.

After the soaking, transfer once again to a blender and whizz again until the mixture is smooth (but grainy).

Strain through a couple of layers of cheesecloth, pushing with the back of a wooden spoon to extract as much of the liquid as possible. Discard the solids.

You can prepare your own coconut milk by using the same rice blender, adding water just enough to cover about 2 cups grated coconut, and whizzing for a minute or so. Strain--and repeat the process. The first collection gives you thick coconut milk; the second gives you thin. You should have about 2-3 cups from this process, but don't worry if you have less. Adjust with cool water.

Add this coconut milk to the rice-melon-seed milk.

Add the sugar, starting with 3/4 cup and then adding the last 1/4 cup to taste.

Chill this mixture in a jar thoroughly, about 5 hours.