In a medium saucepan, combine black rice and water. Bring to a boil, then reduce heat to low, cover, and simmer for 30 minutes.
Add coconut milk, sugar, and salt. Stir well and continue to simmer uncovered for 15-20 minutes, stirring occasionally, until rice is tender and porridge has thickened.
Remove from heat and stir in vanilla extract.
Serve warm, topped with desired toppings such as toasted coconut, mango, or sesame seeds.
Tips
For a thinner porridge, add more coconut milk or water.
Leftovers can be stored in the refrigerator for up to 3 days; reheat with a splash of coconut milk.
This porridge can also be served chilled as a pudding.