Sauce for German Pudding

This is a sherry sabayon: two yolks, sugar and wine whisked over gentle heat until it holds a ribbon. The whole recipe hinges on temperature control, so set up for that before you start.

• The hingeEgg yolks in wine set into a grainy scramble once they pass roughly 180F. Whisk in a bowl over barely simmering water, never in a pan on direct heat, and lift the bowl clear the moment the foam thickens.
• TeacupfulA Victorian teacupful is about 5 fl oz, a quarter of an imperial pint. That is a generous ratio of liquid to two yolks, and the sauce will be light and pourable rather than thick; use 4 fl oz if you want it stiffer.
• Cooking the eggs through"Do not let it get too hot" was aimed at curdling, not safety. If you want the eggs cooked through, whisk the mixture to 160F on an instant-read thermometer and hold it there briefly; it should still be foamy, though at that temperature you are close enough to the setting point that it pays to keep whisking and to lift the bowl if the heat runs uneven.
• Sugar"A little sugar" is left open; 1 to 2 teaspoons per yolk is a reasonable starting point, adjusted to the wine. Dissolve it into the yolks before the wine goes in so it does not sit gritty at the bottom of the bowl.
• The sherryA richer, nuttier sherry such as amontillado or oloroso, or a sweetened cream sherry, suits this better than a bone-dry fino. If you use a cream sherry, reduce the added sugar.
• "Whisk it until it is wanted"The instruction is literal: a sabayon separates within a few minutes of standing. Keep it over the warm water and keep whisking, or make it while the pudding rests from the oven.
• YieldTwo yolks and a teacupful of wine makes enough sauce for about four servings of a steamed or baked pudding.