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Leek Soup
Cut up two onions and fry them till they are brown; you need not use butter, clarified fat will do very well. Clean your leeks, washing them well; cut them in pieces and fry them also; add any other vegetables that you have, two medium-sized potatoes, pepper, salt, and a little water. Let all simmer for three hours, and pass it through a fine sieve. Let there be more leeks than other vegetables, so that their flavor predominates.
A frugal wartime purée with no stock, no butter and no cream — the flavour comes entirely from browning and long simmering. Two things need adjusting: the water quantity is never given, and three hours is far more than leeks need.
- The hinge: brown the onions properlyWith no stock, no cream and butter treated as optional, the only depth in this soup comes from the fond you build frying the onions and leeks. Take the onions to a genuine deep brown over medium heat, then the leeks until their edges colour, before any liquid goes in.
- "A little water" is not a littleThe original quantity is genuinely ambiguous. For two onions, two potatoes and roughly 4–6 leeks, start with about 1 litre (4 cups) of water, keep it barely covering the vegetables, and top up as it reduces.
- Simmering timeThree hours reflects a habit of long, slow cooking, though the recipe gives no reason for it. Leeks and potatoes are fully soft in 30–40 minutes, and prolonged boiling does the leek flavour no favours. Cook until the potato collapses, then stop.
- Clarified fatRendered beef or pork drippings, or clarified butter; the recipe offers it as the cheaper stand-in for butter. Any neutral oil works, but a spoonful of bacon fat or duck fat gets closer to the original taste.
- Washing leeksGrit sits between the layers, and a whole-leek rinse will not reach it. Split the trimmed leeks lengthwise, fan the layers under running water, then slice.
- Sieve or blender"Pass it through a fine sieve" produced a smooth purée by force. A blender or stick blender does the same in seconds; pass it through a sieve afterwards only if you want the leek fibres out entirely.
- SeasoningThe recipe salts along with the pepper before simmering, but a water-based soup like this needs more salt than you expect. Check and adjust at the end, after puréeing, and taste twice.
- YieldUsing the water quantity suggested above, about 1.5 litres — four generous bowls as a first course, or two as a supper with bread.
This comes from The Belgian Cook-Book, compiled in 1915 from recipes collected from Belgian refugees who had fled to England after the German invasion, with the proceeds said to have gone to relief work. That origin explains the shape of the recipe: no butter ("clarified fat will do very well"), no meat stock, no cream, and an instruction to "add any other vegetables that you have." Leeks were the obvious backbone for such a soup — cheap, storable through winter, and grown across the Flemish and Walloon countryside — and versions of this thickened-with-potato leek purée are common to northern French and Belgian home cooking. The insistence that the leek flavour "predominates" is the only luxury the recipe permits itself.