Pour coconut milk (or cream) into a large saucepan over a medium heat.
Add sugar.
Heat the coconut milk, regular milk, and sugar but DO NOT BOIL.
Meanwhile, in a large bowl, whisk the beaten egg yolks with the vanilla extract.
Pour approximately half the hot coconut milk into the egg mixture.
Whisk briskly.
Add the remainder of the coconut milk and sugar mixture.
Pour the combined mixture back into the saucepan.
(Wash out the bowl because you'll need it again in a few minutes.)
Cook the coconut eggnog mixture over a low heat but DO NOT BOIL.
Stir continuously.
Keep stirring until the eggnog thickens slightly - enough to cover the back of a spoon.
Pour and strain the eggnog back into the (washed, rinsed, dried) bowl.
Allow the eggnog to sit and cool utnil it becomes room temperature.
Once cooled, stir through the dark rum.
Cover with cling film and refrigerate for several hours (preferrably overnight).
Just prior to serving, combine the ground cinnamon with the ground nutmeg into a small bowl, then sprinkle a little of the combined spice over the top of each serving of eggnog.
Notes
I love the flavors in this cooked coconut eggnog recipe!