Method
1 Place egg yolks, and sugar in a large, round-bottomed stainless steel bowl. Add grated lemon peel and a pinch of cinnamon and a drop of vanilla extract to the yolk mixture. Pour in the Marsala wine. You can use sweet Vermouth as a substitute for the Marsala.
2 Half-fill a pot with water, bring the water to a simmer and reduce the heat to low. Set the pan or bowl containing the custard mixture over the water; the bottom of the bowl should not touch the water. Whisk the custard mixture, making sure that the water does not boil. This ensures that a gentle, even heat thickens the mixture without curdling it. Whisking traps air in the yolks for a light, fluffy mixture.
3 Continue whisking for about 10 minutes, until the mixture triples in volume, froths up and becomes pale. When it reaches the desired consistency, take the container of custard out of the pot. Slightly thickened, the custard can be used as a sauce. Longer cooking will thicken the custard further, giving it the texture of mousse. Continue whisking for a minute or two to prevent the custard from sticking to its container.
4 Serve the custard while still warm, or, if you want to serve it cool, set it aside for about 15 minutes. Whisk heavy cream until it forms soft peaks; add the whipped cream to the cooled custard and use a whisk to gently fold them together. Reserve some of the whipped cream to serve on top.
Ladle the zabaglione into individual dishes. Serve with whipped cream, berries, and/or cookies such as biscotti.
Serves 6.
