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Leek Soup
Mix two tablespoonfuls of oatmeal with a small quantity of cold water, put it in a saucepan, stir in about one quart of boiling mutton broth, adding it by degrees, then throw in as many leeks as are required, and boil until tender and the liquor is of the consistency of cream. Remove the pan from the fire, stir in the yolks of two eggs beaten up in a little of the broth, turn the whole into a tureen and serve.
A thin oatmeal-thickened broth in the Scottish manner, written for a cook who already knows how many leeks a soup wants. Two decisions are left to you: the quantity of leeks and the fineness of the oatmeal.
- The liaison is the hingeThe egg yolks must go in off the heat, tempered first with a ladle of hot broth as directed. If the pan goes back over direct flame after that, the yolks scramble and the soup turns grainy; hold it below about 180F if you must warm it through.
- Oatmeal, not rolled oatsIn 1896 this would most often mean pinhead or medium oatmeal, which thickens without dissolving. Rolled oats will work but give a softer, cloudier body; slaking in cold water first, as the recipe says, is what keeps it from lumping when the hot broth goes in.
- How many leeks"As many as are required" is genuinely open. For a quart of broth, four to six medium leeks, white and pale green, sliced, gives a soup that reads as leek rather than as gruel.
- Mutton brothMature mutton is scarce in most markets. Lamb neck or shoulder broth is the closest substitute; a good beef or chicken stock works but loses the slight gaminess the dish was built around.
- TimingSliced leeks are tender in 15 to 20 minutes, and the oatmeal needs about the same to lose its raw edge. Cooking well past that dulls the leek flavour to nothing in particular.
- Consistency of creamThis means pouring cream, not whipped — the soup should coat a spoon lightly. If it thickens too far as the oatmeal swells, loosen with more broth before the yolks go in.
- YieldA quart of broth plus leeks serves four as a first course. Season at the end; broth reduced during cooking can carry more salt than expected.
Leeks thickened with oatmeal and finished with egg yolk belong to the Scottish and northern English tradition that also produced cock-a-leekie, where the leek is the vegetable of the poor man's garden and oatmeal does the work that flour or cream does further south. Its appearance in Oscar Tschirky's 1896 collection is a reminder that the book is less a record of what the Waldorf served in its dining rooms than a working compendium in which standard household and European recipes were gathered alongside the hotel's own, and plain broths of this kind sit a few pages from dishes far grander. The egg-yolk liaison is the older technique here: thickening soup with beaten yolks off the fire is generally taken to predate roux-based cookery in European kitchens, and it survives in this soup as a domestic habit rather than a restaurant flourish.