The Italian sauce known as zabaglione is traditionally made with eggs, sugar, and Marsala wine. Because we don't want to overwhelm the sweet flavor of the strawberries, in our version of this ethereal sauce we've substituted Moscato d'Asti wine. This is one of the simplest desserts to put together, and yet its lightness of texture and subtle flavor make it the perfect partner for fresh berries. The zabaglione is meant to be served warm, so the sauce really needs to be made at the last minute - but it only takes 10 minutes to make, so don't despair! For a chilled version of this dessert, let the sauce cool and refrigerate it until completely cold. Whip 1/2 cup of heavy cream until stiff, then fold the cream gently into the zabaglione. By adding the whipped cream, the zabaglione becomes sabayon sauce. Try drizzling the zabaglione with aged balsamic vinegar, in the Italian style, just before serving.
Divide the strawberries among goblets or small bowls.
Place the egg yolks in the top of a double boiler (or in a heat-proof bowl) and whisk to combine. Whisk in the sugar and the wine. Place over gently simmering water (make sure the bottom of the pan or bowl doesn't touch the water) and cook, whisking constantly, until the mixture has tripled in volume and thickened, about 10 minutes. Don’t allow the mixture to get too hot or the eggs will scramble. Remove the bowl from the heat and continue whisking for another minute.
Spoon the warm sauce over the berries and serve immediately. Drizzle with balsamic vinegar, if desired.