Boiled Icing
One cup of granulated sugar One-fourth cup of water White of one egg Boil the sugar and water until it will string when dropped from a spoon. Beat the white of the egg until stiff, and into it gradually beat the syrup. Flavor with any Larkin Flavoring Extract preferred and beat until smooth.
A one-egg-white Italian meringue by another name, and the whole thing hinges on how far the syrup is cooked.
- The syrup stage"Until it will string when dropped from a spoon" is thread stage, roughly 230-235F on a thermometer. For an icing firm enough to hold a swirl and set with a thin crust, take it a little further, to 238-240F (soft ball); stopping short gives a syrupy glaze that never sets.
- Do not stir the syrupOnce the sugar has dissolved, leave it alone and wash any crystals down the pan sides with a wet brush. Stirring or stray crystals will seed the syrup and turn the finished icing grainy.
- Pouring techniqueAdd the hot syrup in a thin, steady stream against the side of the bowl with the mixer running, not into the middle of the whites. Poured straight onto the beater it will fling hardened threads onto the bowl and set on contact.
- Beating timeThe original cook beat by hand until the bowl felt cool. A stand mixer needs about 5-7 minutes on medium-high; stop when the meringue is at room temperature and holds a firm peak. Overbeating past that point dries it out and it will crack when spread.
- Larkin Flavoring ExtractA house brand sold by mail order and long gone. Half a teaspoon of vanilla, almond or lemon extract does the same job. Add it at the end, as the recipe directs, once the icing has stopped steaming.
- StabiliserAn eighth of a teaspoon of cream of tartar beaten into the whites at the soft-peak stage makes the meringue considerably more forgiving, and a pinch of salt sharpens the flavour of what is otherwise very plain sugar.
- Egg white safetyHot syrup at 238F raises the temperature of the whites considerably as it is beaten in, so this is not the same as a wholly raw-egg icing, but the mixture is not reliably pasteurised and the finished temperature varies with how fast the syrup goes in. At thread stage it is more marginal still. Anyone serving the very young, elderly, pregnant or immune-compromised should use pasteurised whites.
- Yield and humidityOne cup of sugar and one white fills and tops a single 8-inch layer, or frosts about a dozen cupcakes; double it for a two-layer cake. Boiled icing weeps and stays tacky in damp weather, so make it on a dry day and use it the same day.
Boiled icing was for a long stretch a common American cake finish, often said to have given way gradually to butter-and-confectioners'-sugar frostings in the early twentieth century. It is the same construction that French and Italian pastry work calls Italian meringue: sugar boiled to a thread and beaten into whites, giving a glossy, snow-white coating that set with a light crust and needed no butter. Its close relative, seven-minute frosting, cooks the same mixture over a double boiler instead. The instruction to flavour with "any Larkin Flavoring Extract preferred" marks this page as belonging to the era of manufacturer-sponsored cookery: the Larkin Company of Buffalo sold soap, extracts and household goods by mail, and recipe pamphlets naming its products were a routine way of keeping the brand in the kitchen.