A dish is always as good as its ingredients. Poor rum will ruin, in my opinion, this cocoa. So if you are going to use rum, use a good quality rum. Bacardi makes a higher end rum, about 40$ a bottle, that serves well. Regular Bacardi rum, Captain Morgans, etc .. I would not use. Neither would I use very high end rum, unless you can afford it. Ron Zacapa aged rum is delicious, but for hot cocoa, I would stick to a less expensive good rum.