Wash and boil beans without salt until really soft.
Allow to cool, then blend till smooth in a blender or food processor with the coconut milk.
Pass through a sieve to get it a little bit smoother and to get some chaff out.(If your blender didn't get it as smooth as you would like.) You will need a spoon to help you while you sieve.
Pour your sieved beans back into the pot, add sugar, and some salt. Then cook on low heat while stirring constantly until it thickens like a light porridge.