Frosting

This is a formula rather than a method — the book assumes the cook already knows how boiled icing works. It is the standard three-part boiled frosting: sugar syrup cooked to the thread stage, poured slowly into a beaten egg white.

• The hinge: syrup temperatureCook the sugar and water without stirring until the syrup will spin a thread from the spoon. The book gives no test or temperature; modern boiled-frosting practice puts this at roughly 238-240F, at the bottom of soft-ball. Undercooked, the frosting stays soupy and never sets; taken much further it tends to grain and stiffen before you can spread it.
• Adding it to the whiteBeat the white to stiff peaks first, then pour the hot syrup in a thin steady stream down the side of the bowl while beating continuously. Dumping it in at once scrambles the white and leaves cooked threads through the icing.
• "Flavoring"Period shorthand for whatever extract was on the shelf, most often vanilla, sometimes lemon or almond. Half a teaspoon is right for this quantity, beaten in at the end once the frosting has cooled to lukewarm.
• Egg sizeEggs of the period generally ran smaller than today's large. One modern large white (about 33 g) is slightly generous for a cup of sugar but works; two whites at this sugar level will give a fluffier, marshmallow-like icing that sets softer.
• Raw-egg cautionHot syrup raises the white well above room temperature but does not reliably pasteurize it. If serving to anyone vulnerable, use pasteurized whites or carton whites, which whip perfectly well for this.
• YieldAbout a cup and a half of frosting — enough to cover the top and sides of one 8-inch layer, or the top of a loaf or a pan of bread pudding.
• Weather mattersBoiled frosting is humidity-sensitive. On a damp day it stays tacky and may weep; cook the syrup two or three degrees higher than usual to compensate.
• Working timeBeat until the frosting holds its shape and loses its gloss, then spread at once. It skins over quickly and cannot be rewarmed.