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Lemon Custard
Pour into a saucepan one quart of milk, the thin rind of a lemon, two bitter almonds, and one-half pound of sugar. Bring the milk to the boil, strain it gradually through a fine sieve into a saucepan over six well-beaten eggs, and stir well until it thickens. Pour it at once into custard-cups or glasses, and serve either hot or cold.
A plain boiled custard of the kind every large hotel kitchen turned out by the tray, but it is flavoured with bitter almonds, which is why it cannot be made today.
- Bitter almonds are the problemBitter almonds contain amygdalin, which releases hydrogen cyanide when the kernels are crushed, chewed or steeped in warm liquid. The dose in two kernels steeped in a quart of milk is small, but the point stands: this is a toxin, its concentration in any given kernel is unknown, and there is no way to measure it in a domestic kitchen.
- Heat does not make them safeBringing the milk to a boil drives off some hydrogen cyanide but does not reliably destroy the amygdalin in the kernel, and the brief infusion here is nowhere near a controlled detoxification. Commercial bitter-almond products are processed specifically to remove the cyanogenic compounds; the raw kernel is not.
- You will not find them anywaySale of raw bitter almonds to consumers is prohibited or tightly restricted in the United States and much of Europe. What is sold as "bitter almond extract" or "bitter almond flavour" is benzaldehyde, with the cyanide removed or never present.
- Do not improvise around itThe rest of the method is an ordinary stirred custard, but a stirred custard is not the reason to keep this page. If you want lemon custard, use a current recipe with a stated egg-to-milk ratio and a finishing temperature.
- On the quantities, for the recordHalf a pound of sugar to a quart of milk is about a cup and a sixth by modern measure, and six whole eggs to a quart is a rich set. "The thin rind" means the yellow zest pared without pith, which is what carries the oil.
Oscar Tschirky ran the Waldorf's dining rooms rather than its ranges, and his 1896 book gathers the standard repertoire of a late-nineteenth-century American hotel kitchen, much of it descended from French practice. This is close kin to crème anglaise under a plain English name — though it uses whole eggs rather than yolks alone — poured into cups and sent out hot or cold as the service required. The pairing of lemon peel with a bitter almond or two was a long-standing European habit: the almond supplies benzaldehyde, the same compound that gives marzipan and cherry-pit flavourings their character, and cooks used it much the way later cooks used a few drops of extract. Cookbooks of the period call for bitter almonds, peach kernels and apricot kernels in similar roles in custards, blancmanges and ratafias, often without comment on the risk, although the toxicity of the kernels was known to chemists by then. Regulation caught up in the twentieth century, and the bottled extract replaced the kernel.