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Rock Cakes, Almond or Cocoa-Nut
Blanch three-quarters of a pound of sweet and three or four bitter almonds, and cut them in pieces the size of a pea. Whisk the whites of three eggs to a firm froth. Stir in three-quarters of a pound of white and sifted sugar, a tea-spoonful at a time, and add quite as gradually the blanched almonds. Lay a piece of buttered paper on a flat tin, and with a fork drop the mixture in little knobs upon it. Bake in a moderate oven. Half a pound of grated cocoa-nut may be substituted for the almonds. Time, twenty to thirty minutes. Probable cost, 1s. 4d. per pound.
This is a meringue-and-almond drop cake of the macaroon family, and it is straightforward baking with one exception: the three or four bitter almonds. That single ingredient puts the recipe out of reach.
- Bitter almonds are the problemBitter almonds contain amygdalin, which the nut's own enzymes convert to hydrogen cyanide on crushing, chewing or wetting. Recipes of this period routinely specify bitter almonds by the number rather than by weight, as here, which leaves the dose entirely dependent on the size and strength of the individual nuts; there is no reliable domestic way to judge it.
- Why baking does not fix itWhy baking may not fix it -- Heat can drive off some hydrogen cyanide, but these are pea-sized pieces of nut in a moderate oven for twenty to thirty minutes, not ground and not boiled. The method cannot be relied on to destroy the glycoside or the cyanide it yields.
- Not the same as almond extractModern bottled almond flavouring is benzaldehyde, either synthetic or steam-distilled from bitter almond or apricot kernels with the cyanide removed. It is not a measured equivalent for whole bitter almonds, and treating it as one turns this into a different recipe.
- Sale is restrictedRaw bitter almonds are not permitted to be sold for food use in the United States, and their sale is restricted in the EU and UK under limits on hydrogen cyanide in foods. If a bag has been obtained anyway, that restriction is the reason.
- Cocoa-nut version, same documentThe coconut variant avoids the toxic ingredient, but it is offered here as a substitution within a recipe whose base instructions are the ones above. For almond or coconut macaroons, use a current recipe rather than adapting this one.
- Reading the cost line"1s. 4d. per pound" is one shilling and fourpence. It is a period price, not a measurement.
This is a drop meringue of the macaroon family: egg white, sugar and nuts, no flour, no butter beyond the greased paper. The "rock" appears to describe the shape, the rough knob left by a fork rather than a piped or moulded biscuit. Bitter almonds, from a variety of Prunus dulcis distinct from the sweet nut, were a long-established flavouring in British and French confectionery, sold by grocers alongside sweet almonds and used a few at a time to sharpen an otherwise bland almond paste. The practice faded through the twentieth century as commercial benzaldehyde essence, cheaper and predictable, replaced them.