In a saucepan combine the sugar, the milk, and the cream and scald the mixture over moderate heat, stirring.
In a large bowl beat the egg yolks until they are light and thick and pour in the milk mixture through a fine sieve in a stream, stirring.
Cook the mixture moderate heat, stirring, until it coats the spoon. Transfer the custard to a metal bowl set in a bowl of ice and stir until it is cool.
In a small stainless steel or enameled saucepan reduce the Black Seal Rum over moderately high heat by half, taking care it does not ignite. Allow it to cool.
Stir the Black Seal Rum and the crystalized ginger into the custard and chill the mixture, covered, for 2 hours.