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Potage au Tapioca
Ingredients.
One pint of White Stock.
A quarter of an ounce of crushed Tapioca.
Two yolks of Eggs.
One gill of Cream or Milk.
Salt. Put the stock on to boil. When boiling, shake in the tapioca and stir until cooked. Beat the yolks and cream together and strain into another basin. Add the soup, when it is just off boiling point, slowly to this basin. Then pour the soup back into the saucepan, place it on the fire, and stir carefully until the eggs are cooked. This soup requires care not to curdle the eggs.
A classic egg-and-cream liaison soup: the tapioca does the body, the yolks do the finish. Everything depends on the temperature at the end.
- The hinge: never let it boil after the yolks go inOnce the liaison is added the soup must not exceed about 180F/82C, or the yolks scramble and the soup breaks into threads. Stir constantly over low heat until it thickens enough to coat the back of a spoon, then pull it off immediately.
- A gill5 fl oz in British measure, about 140 ml (a little over half a US cup). Against a pint of stock that is roughly one part cream to four parts stock.
- Quantities and yieldA pint of stock plus a gill of cream gives two modest servings, or four as a first course in the small cups such soups were served in. A quarter ounce of tapioca is about 7 g, roughly two teaspoons: it is there to give a faint body, not to make a pudding.
- Crushed tapiocaTapioca was sold as pearls, which could be crushed at home, and also ready-crushed. Modern small pearl tapioca, crushed briefly in a mortar, or the fine granulated tapioca sold for thickening, both work. Instant tapioca dissolves faster and needs watching.
- Cooking the tapioca"Stir until cooked" means until the granules turn from white and opaque to clear, generally 10 to 15 minutes at a bare simmer for crushed pearl, a few minutes for granulated. Undercooked tapioca stays chalky in the mouth.
- White stockAn unbrowned stock: veal or chicken bones, aromatic vegetables, no roasting and no colour. A good unsalted chicken stock is the modern equivalent; avoid a dark brown stock, which would fight the pale finish the recipe is after.
- TemperingThe instruction to add the hot soup slowly to the yolk-and-cream basin, rather than the reverse, is the whole safeguard. Pour in a thin stream while whisking, and only when the soup is off the boil.
- SeasoningSalt is the only seasoning given. A scrape of nutmeg or white pepper is period-appropriate if you want it.
Thickening soup with beaten egg yolks and cream — a liaison — is one of the oldest finishing techniques in French cookery, and by the late nineteenth century it was familiar in British kitchens that aspired to "high class" work. Tapioca, the starch extracted from cassava root, reached British grocers through nineteenth-century colonial trade and was valued for giving a clear soup body without clouding it or announcing itself as flour. Named soups of this type — potage au tapioca, consommé au tapioca — filled the light-soup slot on a formal menu, often served in cups rather than plates. The closing warning about curdling reflects how easily the liaison breaks.