Shake and strain all but the bitters - float this on top. To shortcut the ginger infused rum, I did a rapid infusion with an ISI cream whipper and fresh ginger
Please correct if you know better, especially if you are Greg.
Original calls for ginger infused rum; as a shortcut I did a rapid infusion of fresh ginger in an ISI cream whipper. Original has cardamom-sugar rim instead of the bitters.