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Soup à la Soubise
Thinly slice two Spanish onions, and cook ten minutes in one -fourth cup butter, stirring constantly. Add one quart
What survives here is the foundation of a classic onion soup: two large onions sweated in butter before liquid goes in. The notes below cover that stage and what a soubise expects of it.
- Spanish onionsThese are the large, mild, straw-skinned onions still sold as Spanish onions; a good-sized one runs to something like three-quarters of a pound to a pound. Two of them sliced should give roughly five to six cups, a generous base for a quart of liquid.
- Butter quantityOne-fourth cup is 4 tablespoons, 2 oz, about 57 g. That is a lot of fat for two onions and it is deliberate: the butter carries the sweetness and later thickens the purée.
- Ten minutes, stirring constantlyThe intent is to soften the onions without browning them. A soubise is meant to be pale, so keep the heat moderate and pull back the moment the slices start to colour at the edges; ten minutes over too high a flame will give you a brown onion soup instead.
- What the quart isThe text breaks off before the liquid is named; in soups of this type it is usually white stock, milk, or a mixture of the two. A soubise is finished as a smooth purée, so the onions are cooked until collapsing, then sieved and thinned to the consistency of thick cream.
- SeasoningOnion purées taste flat without salt and a little white pepper, and they take well to a scrape of nutmeg. Season after the purée is thinned, not before, since reducing concentrates whatever you have added.
- YieldA quart of liquid plus the onions gives four to six cups of finished soup, or four servings as a first course.
Soubise in French cookery denotes an onion preparation, the term deriving from the family name rather than being a French word for onion: a soubise sauce is an onion purée bound with rice or béchamel, and a soup à la soubise is the same idea thinned to spoon consistency. The name is generally traced to the household of the 18th-century Prince de Soubise, whose kitchen is credited with the preparation, though such attributions in classical French cooking are traditional rather than documented. Pale, sieved vegetable purées like this one were the polite, digestible opening course of a turn-of-the-century American dinner, cheap to make from a single vegetable and butter, and dressed up with a French name that told a hostess's guests she knew what she was serving.