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Frost, or Icing, for Cakes
Put two pounds of what is called icing sugar into a bowl, and mix with it the whites only of two, or, if necessary, of three eggs, or even four, and a few drops of lemon-juice. The fewer eggs the better. The egg-whites must not be beaten. Stir the sugar vigorously till there is a smooth thick paste that will not run; this will call for both strength and patience. Lay the icing on the cake with hands dipped frequently into cold water, and smooth it with an ivory knife dipped in cold water. Let it harden in a cool oven.
This is the royal icing of the Victorian confectioner: pure sugar and unbeaten egg white, worked by hand until it stiffens. The method is sound, but the icing is never cooked, and that is where it fails a modern kitchen.
- Why the cautionThe egg whites are stirred in raw and stay raw. A "cool oven" dries the surface but does not bring the interior of the icing anywhere near a temperature that would kill Salmonella, and the icing then sits on a cake at room temperature for days. Anyone wanting royal icing today should follow a current recipe built on pasteurised whites or meringue powder.
- Icing sugarThe same thing as confectioners' or powdered sugar, though the Victorian article was simply loaf sugar pounded and sieved, with no cornflour anti-caking agent. Modern icing sugar, cut with starch, may behave a little differently in the mixing.
- Two pounds is a great dealRoughly 7 to 8 cups of sifted icing sugar. That is enough to cover and decorate a large celebration fruit cake rather than a domestic layer cake.
- "The egg-whites must not be beaten"This is the hinge of the recipe and the reason it demands "strength and patience." Leaving the white unbeaten avoids working air into the paste, which tends to give a denser, harder-setting icing than a whipped one.
- The egg count is deliberately vagueTwo, three, or even four whites are offered, presumably because egg size and the dryness of the sugar both varied. "The fewer eggs the better" means: add white a little at a time and stop the moment the paste holds its shape.
- Lemon juiceA few drops in this quantity is too little to flavour the icing; acid is generally credited with whitening it and helping it set firm.
- Ivory knifeA palette knife of bone or ivory. Non-metal blades were commonly preferred for acidulated work, probably to avoid discolouration from the steel of the period; modern stainless steel raises no such problem.
- "A cool oven"The barely-warm oven left after baking; period sources generally put a cool oven very low, and here it is used only to dry the surface. It was never intended as cooking, which is precisely the difficulty.
Hard white icing over rich fruit cake became the standard finish for wedding and christening cakes in nineteenth-century Britain, and this is the confectioner's version set down for a household with a strong-armed cook. The extravagance is part of the effect: two pounds of refined white sugar, laid on thick and burnished smooth, advertised both the expense of the sugar and the labour available to work it. The instruction to work the icing with wet hands rather than a machine is a reminder of how recent electric mixers are; the same paste that took "strength and patience" here is now the work of a few minutes in a stand mixer. The name "royal icing" is generally traced to its use on grand ceremonial cakes of the period, though the association is traditional rather than documented to any single occasion.