Soubise Sauce
Peel and boil three large white onions in salted water. When very tender, press through a sieve and add one pint of white sauce. Season with salt and pepper and simmer for five minutes.
A two-ingredient sauce that lives or dies on the onions: they must be cooked to complete collapse and kept pale, or the sauce turns sweet-brown and grainy.
- The hinge — no colourSoubise is a white sauce. Boil the onions gently, covered, and do not let them catch or brown at any stage; a blond onion gives a beige sauce and loses the point.
- White sauceThe book means a plain béchamel and gives no proportions. A usual range for 1 pint (2 cups) milk is 2 to 4 tbsp each of butter and flour, cooked out so no raw flour taste remains; the heavier proportion stands up better to the water in the onion purée. Make it before the onions finish so both are hot when combined.
- Three large white onionsSomething like 1½ to 2 lb peeled, depending on what the book counted as large. Yellow onions work but are sweeter and darker; Spanish or true white onions stay milder.
- Boiling versus sweatingBoiled onions carry a lot of water into the sauce. Drain them very well and press hard through the sieve, or sweat them in butter with a splash of water instead for a fuller flavour.
- Sieve or blenderA fine sieve gives the smoothest result and removes any fibrous rings. A blender is faster but can whip air into the purée and change its texture — pulse rather than run it.
- Five minutes, no moreThe simmer is only to marry the two and drive off excess water. Long cooking dulls the onion and risks scorching the milk solids on the pan bottom.
- SeasoningSalt, white pepper and, if liked, a scrape of nutmeg. A spoonful of cream stirred in off the heat is a common finish for such a sauce, though this recipe does not call for it.
- Yield and serviceMakes roughly 1½ pints, enough for six to eight. Serve hot with roast game birds, mutton, lamb or veal; it will thicken as it stands, so loosen with a little hot milk.
The name is generally traced to the Princes de Soubise, an eighteenth-century French noble house — the attribution is traditional rather than documented, and cooks have long argued over whether a true soubise is an onion purée bound with béchamel or with rice. A pale, sweet onion sauce softens the strong, lean flesh of birds and venison in a way that a sharp fruit sauce does not. The recipe is reduced here to two lines that assume the reader already keeps a pint of white sauce within reach.