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Rhubarb Soup
Take half a dozen sticks of fine young rhubarb, peel them, and cut them into short lengths. Throw these into a quart of good veal or beef stock, and add a moderate sized onion, two thin slices of bread, and a little salt and pepper. Let the liquor boil, remove the scum as it rises, and simmer the soup gently until the fruit is quite tender. Strain it, and serve with toasted sippets. Time to simmer the soup, about half an hour. Sufficient for five or six persons.
A savoury soup, not a dessert: the rhubarb here works as an acid, the way lemon or sorrel would. Two things decide whether it succeeds — the quality of the stock and knowing when to stop cooking.
- How much rhubarbSix sticks of "fine young" rhubarb is roughly 12-14 oz (350-400 g) trimmed. Early forced stalks, thin and pink, are what the recipe assumes; late-summer stalks are coarser, greener and much more sour, so taste before committing the whole amount to the pot.
- Leaves off, alwaysUse the stalks only. Rhubarb leaves contain high levels of oxalic acid and are not food; cut them away and discard them before you peel. The peeling of the stalks themselves is only about stringiness and can be skipped on tender stems.
- The stock is the dishA quart here is the imperial quart, 40 fl oz or about 1.1 litres, not the US 950 ml. With only rhubarb, onion and bread in it, a weak stock gives a thin, sour result. Use a properly gelatinous veal or beef stock, or a good unsalted commercial one reduced a little to concentrate it.
- Why the bread is thereTwo thin slices of bread act as the thickener, in the older manner of bread-thickened soups; the recipe itself gives no reasoning. Use plain white bread with the crusts off; a modern sourdough or wholemeal loaf will push its own flavour forward and muddy the soup.
- Don't overshoot the half hourRhubarb collapses fast. Thirty minutes of gentle simmering is enough for the stalks to fall apart and give up their acid; longer and the soup turns flat and stewed rather than sharp. Start checking at fifteen minutes with young stalks.
- Pan and strainingCook in stainless steel or enamel, not bare cast iron or unlined aluminium — rhubarb's acidity draws a metallic taste out of both. Strain through a sieve, pressing the solids to get the pulp through, and discard the onion and the spent fibre.
- SippetsSippets are small triangles or dice of bread toasted or fried in butter, added at the table so they stay crisp. Cut them no larger than a thumbnail and hand them separately.
- Seasoning at the endSeasoning -- The recipe salts and peppers at the outset, but taste and adjust again after straining, since the acid can make an underseasoned soup read sharper than it is. A little sugar, a spoonful at most, rounds it without turning it sweet. Yield is given as five or six, which is right for a first course.
Rhubarb entered English kitchens as a medicinal root long before it was eaten as a stalk — the dried rhizome was a purgative imported from Asia via Russia and the Levant, which is why old herbals speak of "Turkey rhubarb" and "Russian rhubarb." Culinary rhubarb only became commonplace in Britain in the nineteenth century, once cheap sugar and the forcing sheds of the West Riding made it a spring staple. That rhubarb should turn up in a soup at all reflects an older habit of treating tart fruit as a seasoning: sorrel, gooseberry and rhubarb all appear in Victorian books as acids for stock and for rich meats, in much the same role a squeeze of lemon plays now. The bread-thickened, strained, sippet-garnished formula is the standard Victorian purée template, applied here to a fruit that was by then abundant and cheap.