The original recipe calls for a smaller 22.5ml (¾oz) measure of tawny port (rather than equal parts of the three main ingredients), which produces a potent...
A decent cocktail - but I think it is a little tilted towards the cognac (not a spirit I favor). The fruit of the cognac and the maraschino are very nice, but they erase the port, and the rum notes are in the distant background.