Whisk all the ingredients except the cream together and strain into a mixing bowl. Set the bowl over a pan of simmering water and whisk constantly until the mixture is light and fluffy and forms a slowly dissolving ribbon on the mixture when the whisk is lifted. Spoon the zabaglione into bowls or goblets and serve warm. Or refrigerate until cold, beat the cream to stiff peaks, and fold into the cooled sabayon. Cover and refrigerate until serving time. Warm or cold, this is excellent with fresh berries or peaches.