Iced Madeira Sauce

A frozen wine sauce built on the same principle as Italian meringue: hot syrup beaten into egg whites, then folded into a slush of chilled juice and wine. The original assumes an ice-and-salt freezer, which is the only real obstacle.

• The hinge: pour the syrup slowlyThe boiling syrup must go into the whites in a thin stream while beating hard, or it will set the whites into threads of cooked albumen. The hot syrup does warm the whites, but this is a thin syrup boiled only briefly, so the mixture should not be assumed to reach a pasteurising temperature; use pasteurised whites if that matters to you.
• Freezing the juice and wineAlcohol and sugar both depress the freezing point, so the wine-and-juice mixture will never go hard. Pour it into a shallow metal pan, put it in the freezer, and scrape with a fork every 20 minutes for about 2 hours until it is a coarse slush. An ice cream machine handles it in 15-20 minutes.
• "A pan of salted ice-water"This is simply an ice bath; the salt drops the water below 32F so it chills faster. A bowl of ice and water with a good handful of salt does the same job. Beat the meringue continuously until it is cold, or it will weep.
• The syrup is thinner than you expectHalf a cup of sugar to a cup of water is a light syrup, and the recipe wants it only brought to a boil, not reduced to a thread. Boiling it down will make the finished sauce cloyingly sweet and stiff.
• MadeiraUse a drinkable bottle-aged Madeira, ideally a medium style such as Verdelho or Bual. Avoid supermarket "cooking Madeira," which is salted and will show badly in a cold sweet sauce.
• Assembly and holdingFold the cold meringue into the frozen juice and wine rather than stirring, and serve within an hour. Left in the freezer it separates into a foam layer over an icy one; a brief whisk brings it back.
• Yield and servingMakes roughly 2 to 3 cups of light, foamy sauce, enough for six to eight. Sauces of this type were commonly served over hot puddings, where the contrast of temperatures is the point, though this recipe itself says nothing about how to serve it.