For the port zabaglione, grate the zest from the orange and squeeze the juice from the orange. Put both in a wide bowl with half of the sugar.
Whisk in the port and yolks. Place the bowl on a lightly simmering water bath and whisk until the mixture is quite frothy and doubles in size.
Then immediately pour the zabaglione into a bowl of ice cold water. When the cream is nice and cool, it is ready.
Preparation Tip:
The port wine zabaglione can be refined or decorated as desired before serving.