Your choice of rum in this island-inspired Old Fashioned will set the tone and flavor of either sweet or earthen. An aged Barbados will bring flavors of mystical vanillas, whereas a grassy Martinique will make for bright green freshness.
Muddle bitters and sugar, then add water. Fill the glass with a large cube and add rum. Stir to combine. Express the orange peel over the glass then drop it in.