Mushroom Sauce

Sauce aux Champignons (mushroom sauce) teaches a stern, useful truth: the base must begin stiffer than the sauce you want, because mushroom liquor brings flavor and loosens it at once. C'est la même grammaire across the classical derivatives. Build a proper foundation, introduce the defining flavor without drowning it, then finish with enough restraint to preserve both.

The brigade formula assumes a saucier on staff, stock never off the fire, and finished Allemande or fish velouté waiting beside a bowl of decoratively channelled mushroom heads. At home, one prepared base, a covered sauté pan, and a heavy saucepan do the same work. This version keeps the book's exact proportions: eight ounces of mushroom caps and one-fifth pint of their liquor for every pint of base. The channelled decoration is brigade scaffolding, so it may go; the firm caps, captured liquor, and late addition are the dish and must stay.

Cook the mushrooms only until tender at the edges, reserve every drop of their liquor, and return the caps at the finish so they remain plump rather than surrendering themselves to the sauce. Before you touch the pan, test the base: it must coat the spoon heavily, because no amount of hurried boiling will replace that necessary body.