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Lemon Cream Sponge
Flavour a pint of cream with the rasped rind of a lemon, and sugar to taste. Set it in a warm corner of the stove, but do not let it boil. Dissolve half an ounce of isinglass separately in a little milk, and add it to the cream. Set the mixture aside to get cold. Add the strained juice of a lemon, and the beaten white of an egg, and whisk thoroughly.
This is a cold set cream, and nothing in it is ever cooked. That single fact is what rules it out, but the ingredient list also needs translating before the instructions make sense at all.
- The raw egg whiteThe beaten white goes into a mixture that has already been cooled, and the dish is then left to set and served cold. No stage reaches a temperature that would deal with Salmonella, which can be present on the shell and in the white as well as the yolk. A raw white whisked into a chilled cream and eaten by children, the elderly or anyone pregnant is a risk the original author had no way to assess; use a current recipe built on pasteurised egg white or an eggless base.
- The cream is warmed, not scalded"Set it in a warm corner of the stove, but do not let it boil" gives neither a temperature nor a time, and how hot the cream actually got would have varied with the stove. Nothing in the wording guarantees a pasteurising heat, and with the later addition of raw white there is no stage in the method that can be relied on to make the finished cream safe.
- IsinglassA collagen setting agent made from the swim bladders of sturgeon and other fish, sold in shreds or sheets and dissolved in warm liquid. Half an ounce is about 14 g. It has effectively vanished from grocery use, survives mainly as a fining agent in cask beer and wine, and does not swap gram for gram with modern gelatine or agar.
- Rasped rindRind removed with a rasp or grater, or by rubbing the whole lemon against a lump of sugar. It means zest only, with none of the white pith.
- PintIn a British book this is an imperial pint of 20 fl oz, roughly 570 ml, not the American 16 fl oz.
- Why the juice goes in lastThe acid is added only once the cream is cold. Lemon juice stirred into hot or warm cream is liable to curdle it, which is a plausible explanation for the order, though the recipe does not say so.
Lemon creams belong to a long line of English "creams" and "whips" that runs from the seventeenth-century banquet course through to the Victorian supper table: cream flavoured with citrus, sweetened, lightly set, and served cold in glasses or turned out of a mould. Before commercial powdered gelatine became cheap and reliable in the later nineteenth century, the setting agents available to a cook were calves' foot jelly, hartshorn shavings and isinglass, and isinglass was prized because it was the cleanest tasting and the clearest of the three. Its decline in the kitchen has more to do with the industrialisation of gelatine than with any change in taste. The "sponge" in the title refers not to cake but to the aerated texture the whisked white gives as the mixture sets.