Hot Icing
Dissolve one pint powdered sugar in two or three tablespoonfuls water, and boil.
Beat the whites of four eggs to a strong froth; add the hot sugar, stirring in till smooth. Beat about two minutes and flavor to your taste, spread on the cake, and put in a hot place.--Mrs. P.
This is a boiled icing — what a modern pastry kitchen would call an Italian meringue — written in the compressed shorthand of a period receipt book. Two details the original omits, the syrup temperature and the sugar's identity, decide whether it works.
- The hinge: how far to boil the syrupThe receipt says only "boil," but for an icing of this kind the syrup is normally taken to about the soft-ball stage, roughly 238-240F on a thermometer. Poured in much cooler, the icing tends to stay loose and weeping; boiled well beyond that it stiffens fast and may set before it can be spread.
- "Powdered sugar" is not confectioners' sugarIn nineteenth-century American usage powdered sugar meant granulated sugar ground fine, before the days of anti-caking starch. Use ordinary granulated sugar here. Modern confectioners' sugar contains cornstarch and will make a cloudy, slightly pasty syrup.
- A pint of sugarMeasured by volume, a pint is 2 cups, roughly 14 oz / 400 g of granulated sugar. With 2 to 3 tablespoons of water that is a very stiff mixture at the start; stir only until it dissolves over the heat, then stop stirring so it does not crystallize on the pan sides.
- Adding the syrupPour it into the beaten whites in a thin, steady stream down the side of the bowl with the mixer running. Dumped in at once it cooks the whites into threads and the icing goes grainy.
- "Beat about two minutes"With a stand mixer expect 5 to 7 minutes, until the bowl is no longer warm to the touch and the meringue holds a firm, glossy peak. Icing spread while still hot will slide off the cake.
- FlavoringAdd it at the end, off the heat. Period flavorings for such an icing were vanilla, lemon, rosewater or almond; a teaspoon is enough for this quantity.
- "Put in a hot place"Most likely the warming shelf of a range, to dry the surface to a thin crust. A very low oven for a few minutes will do something similar, as will leaving the cake uncovered in a dry room.
- Yield and keepingEnough to cover the top and sides of one 9-inch layer cake, generously. Boiled icing is at its best the day it is made; by the second day it weeps and the crust cracks, and it does not survive refrigeration.
- EggsThe hot syrup partly cooks the whites, but an Italian meringue is not reliably pasteurized. If the syrup is underboiled the whites stay close to raw, which matters for anyone who should avoid raw egg.
Boiled icing was one of several common American cake finishes through the second half of the nineteenth century, alongside uncooked egg-white icings and plain water icings: a cook made a smooth, spreadable coating by cooking sugar to a syrup and whipping it into egg whites. Housekeeping in Old Virginia (1878), compiled by Marion Cabell Tyree from contributions by some 250 Virginia housekeepers, is full of these signed fragments — "Mrs. P." is one of many women whose receipts were gathered rather than invented by the editor, and the terseness is the point: it was written for someone who already knew what a sugar syrup should look like when it was ready. The same technique, under the name Italian meringue, is still the base of the buttercreams built on cooked syrup.