Bring the coconut milk to a boil without stirring. Then, cook, stirring, until the oil separates from the milk solids. Lower heat and cook, stirring now and then, until the milk solids turn brown - about 45 minutes.
Turn off heat, and scoop out the browned milk crumbs with a strainer. Spread the crumbs on absorbent paper towels to drain excess oil. Store in a clean jar. Reserve coconut oil for other uses.