Home › Frostings › Boiled Frosting
Boiled Frosting
2 cups sugar 2 teaspoons flavoring 1 cup water Heat sugar and water to boiling, stirring occasionally until the sugar dissolves. Then boil without stirring until the syrup threads when dropped from the end of a spoon or fork or until it forms a soft ball when dropped into cold water. Flavor, and pour the frosting over the cake, using a silver knife to guide it over the sides of the cake. If the frosting becomes granular, add a few drops of boiling water.
This is a poured sugar icing rather than the egg-white boiled frosting most cooks know — no meringue, just syrup cooked to the soft-ball stage and poured while hot. Success or failure turns almost entirely on controlling crystallization.
- The hinge: do not stir after boiling beginsOnce the sugar has dissolved, stirring drags crystals back into the syrup and the frosting sets grainy. Wash any crystals from the sides of the pan with a wet pastry brush and leave it alone.
- Soft ball, in numbersThe soft-ball stage is usually given as 235-240F on a candy thermometer. The thread test named in the original is conventionally a slightly lower stage, so the two are not quite interchangeable; if you use a thermometer, check it in boiling water first in case its calibration is off.
- Flavoring quantityTwo teaspoons is generous for 2 cups of sugar. The recipe does not say what the flavoring is, though an extract such as vanilla or lemon would be typical. Add it off the heat, as the original's order implies, or much of the volatile flavor boils away.
- The silver knifeA silver knife was simply the thin, broad-bladed tool a period household had to hand; an offset spatula or the back of a table knife does the same job. The point is speed, not the metal.
- Work hot and fastThis icing begins to set within a minute or two of pouring. Have the cake on a rack over a tray, pour into the center, and let it flow rather than trying to spread it repeatedly.
- Rescuing a granular batchThe few drops of boiling water do work, but only if added immediately and worked in gently. Once the frosting has fully set gritty, the usual remedy is remelting it with a spoonful of water and reheating to the soft-ball stage.
- YieldRoughly enough to glaze the top and sides of one 8- or 9-inch layer cake, or the top of a 9x13 sheet; the recipe itself gives no yield. It sets firm and opaque rather than staying soft.
- HumiditySugar syrups pick up moisture from damp air; on a humid day the glaze may stay tacky for hours. Cook to the upper end of the range in wet weather.
History: The technique is the confectioner's sugar-boiling craft scaled down to a home cook's saucepan -- essentially a poured fondant. "Boiled frosting" in later American books usually means the egg-white version, so this earlier, plainer sense of the term is worth noting so the recipe is not mistaken for an incomplete one.