Purée à la Palestine

The book gives quantities only, in the shorthand of a professional kitchen where the method for a purée soup was assumed. The proportions are sound, so the notes below cover the units, the vegetable and the working order the list implies.

• Jerusalem artichokes are not artichokesThey are the tubers of Helianthus tuberosus, sold now as sunchokes. Two pounds untrimmed yields roughly 1 1/2 lb peeled; the knobbly skins can be left on if scrubbed hard, though the finished purée will be greyer.
• Imperial measuresIf this is a British book, a quart is 40 fl oz, not the American 32, and the half pint of cream is 10 fl oz rather than 8. Scale up US measures by a quarter if you want the intended richness.
• White stockAn unbrowned veal or chicken stock, made from bones blanched rather than roasted. A light chicken stock is the nearest supermarket equivalent; avoid anything dark or heavily reduced, which will overwhelm the artichoke.
• The order of workSweat the sliced tubers in the 2 oz butter over low heat without colouring, add the stock, simmer 20-25 minutes until collapsing, then purée and pass through a fine sieve. Blenders alone leave a slightly fibrous texture.
• Do not boil after the creamAdd the cream at the end, off the heat or over the barest simmer. A hard boil can split it.
• Keeping the colourPeeled sunchokes brown within minutes. Drop them into water with lemon juice or vinegar as you go if you want a pale ivory soup rather than a beige one.
• SeasoningThe list mentions none. Salt, white pepper and a little lemon at the finish are conventional for a purée of this kind; white pepper keeps the specks out.
• YieldAbout 2 1/2 pints of finished soup, or four to six servings as a first course.
• One practical warningSunchokes store carbohydrate as inulin, which many people digest poorly. A cup of this soup is a reasonable portion for a first attempt.