Pour coconut milk in a saucepan on stovetop. Place chocolate chips in a heatproof bowl and place over coconut milk. This will act as a double boiler. Heat on medium heat until coconut milk comes to a simmer, and chocolate chips are melted slightly.
Remove both from the heat, and pour coconut milk over chocolate chips to finish melting. Using a spatula, mix until smooth.
Add spiced rum, vanilla extract, and salt. Mix thoroughly. Pour into an 8x8" glass baking dish, or similar size. Cover and put in the refrigerator to set.
Once mixture is set, use a melon baller or spoon to form balls. Roll balls in your hands, then into cacao powder. Roll again to give a more polished look, if desired. Refrigerate.