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Brown-Sugar Frosting
1 cup brown sugar
1 teaspoon vanilla or ½ tea- ½ cup water spoon lemon extract
2 egg-whites
Make a sirup of the sugar and water and cook to the soft-ball stage (238° F.). Remove from the fire and cool while the eggwhites are beaten, then pour the sirup in a thin stream on to the stiff whites, beating the mixture constantly until thick enough to spread. Add the flavoring. Chopped nuts may be stirred into the frosting just before spreading.
This is an Italian meringue in all but name: hot sugar syrup whipped into beaten whites. Two things decide whether it works — the temperature of the syrup and how it meets the whites.
- 238°F is not negotiableUse a candy thermometer and take the syrup off at 238°F (soft-ball), as the recipe directs. Much below that and the frosting tends to stay soft and weep; much above and it can set before you can spread it.
- Ignore "cool" — pour it hotThe recipe says to cool the syrup while the whites are beaten, which may reflect no more than the pace of hand-beating. Modern practice is to have the whites already at stiff peaks and pour the syrup in while it is still hot, since hot syrup is what cooks and stabilises the meringue.
- Pour down the sideAim the thin stream at the inside of the bowl between the whisk and the wall. Syrup hitting the moving whisk flings into threads that harden on the sides and never dissolve.
- Brown sugarLight brown gives a caramel-coloured frosting; dark brown gives a stronger molasses flavour and a greyer cast. Pack it when measuring — 1 cup is about 7½ oz / 210 g. Brushing the pan sides down with water while the syrup boils is a useful precaution against stray crystals.
- Egg whitesTwo whites from modern large eggs are about 2½ fl oz / 70 g. Whip to firm but not dry peaks; over-beaten whites break up when the syrup goes in. Whites from eggs a few days old whip higher than very fresh ones.
- Beating timeExpect 7 to 10 minutes of steady beating after the syrup is in, until the bowl is only just warm and the mixture holds a ridge. Stopping early leaves a frosting that slides off the cake.
- Raw-egg noteThe hot syrup heats the whites substantially but does not reliably pasteurise them. Anyone cooking for the very young, elderly, pregnant or immune-compromised should use pasteurised egg whites.
- Weather and keepingBoiled frostings sulk in humid weather and will stay tacky. Spread it as soon as it is thick — it firms fast — and use the cake the same day; by the second it forms a dry crust over a softening interior.
- YieldEnough to cover an 8-inch cake, or to frost about a dozen cupcakes. Chopped walnuts or pecans, about ½ cup, are a common addition.
Boiled or "soft-ball" icings were widely used in American cake decorating from the late nineteenth century until buttercreams took over after the Second World War, and this brown-sugar version is essentially the same preparation that later cookbooks call sea-foam frosting. It belongs to a moment when the candy thermometer was becoming a middle-class kitchen tool: earlier books tell the cook to test the syrup by dropping it into cold water, while the Butterick editors could print a number and, one imagines, expect it to mean something. Butterick, better known for dress patterns, published household compendiums as part of the same project of instructing the American housewife in system and standards, and precise temperatures would seem to fit that tone. The brown sugar here carries its own flavour into a frosting that needs no other.