Potage Compiègne

Potage Compiègne (light Soissonnaise white-bean purée with buttered sorrel and chervil) teaches the difference between a purée and a paste. Light, in the classical language, means flowing and delicate, not timidly enriched. The beans give the soup its body, butter gives it sheen, and sorrel keeps every spoonful awake.

The original entry assumes a light Purée Soissonnaise already waiting, a saucier free to pass and butter it at the last moment, and a stockpot never off the fire. At home, good canned white beans and unsalted light stock provide the honest equivalent in one saucepan. The separate purée station is brigade scaffolding and can go; passing the beans until smooth, finishing them generously with real butter, and preserving the exact three tablespoons of buttered sorrel are the dish and must stay. One cook, one stove, one evening.

Make the purée thinner than instinct first suggests, because beans continue to tighten as they stand. The deciding moment comes when you monter au beurre off the heat: whisk in the cold butter until the surface gleams, then never let the soup boil again.