Combine the chocolate and butter
over a hot-water bath.
Combine the egg yolks with the water and 1 ounce sugar and whisk over a hot-water bathe to 145 degrees F for 15 seconds. Remove from the heat and whip until cool.
Combine the egg
whites with the remaining 1 ounce sugar and whisk
over a hot-water bathe to 145 degrees F. Remove the whites from the heat and beat to full volume. Continue beating until cool.
Using a large rubber spatula
, fold the egg whites into the egg yolks.
Fold the butter-chocolate mixture into the egg mixture.
Fold in the whipped cream
. Add the rum
, to taste.