Clean and rinse the black rice well. You can soak it overnight to soften it if you want. Boil/cook the rice in water using a ratio of 1:7 or 1:8 of rice to water. Sing says to cook it just like you would congee. For those of us who have never cooked congee: boil the rice until the grains are tender, NOT until the water is absorbed. This is supposed to be a soupy dish.
After the boiling is done, or just as it is about to finish, add sugar to taste - keeping in mind that Southeast Asian desserts tend to be syrupy sweet. If using it, add just a few drops of the pandan extract/essence to taste. If using real pandan leaf, break it open so the flavor comes out and throw it in like a bay leaf, be sure to remove it when through.
You can serve this dessert either hot, room temperature, or chilled. Ladle it out into a bowl and add some coconut milk to taste (they way you'd add whipped cream). Sing recommends adding just a wee bit of salt to the coconut milk.
You could also try adding Asian red beans (not like kidney beans.) Start with dry ones and soak with the rice overnight before boiling.