Sauce Normande — Normandy Fish Velouté

Ingredients

• For the fish velouté base
• 30 g unsalted butter, for the roux
• 30 g plain flour, for the blonde roux
• 500 ml fumet de poisson, well-made, strained
• For the mushroom essence
• 100 g white mushrooms, sweated in butter and lemon juice until their liquid runs clear
• 15 g unsalted butter, for sweating
• 1 tsp lemon juice
• For the oyster liquor
• 60 ml oyster liquor, from freshly shucked oysters, strained through fine cloth to remove grit
• 60 ml mussel cooking liquor, if available, strained; optional
• For the liaison
• 3 egg yolks
• 100 ml heavy cream, high-fat; crème fraîche may replace part of the quantity
• For the finish
• 50 g cold unsalted butter, cut into small cubes, for mounting

Method

1. 1
   Make a blonde roux from 30 g butter and 30 g flour in a heavy saucepan over moderate heat. Cook, stirring, until the roux is pale gold and smells faintly of biscuit. Add the fish fumet gradually, whisking to prevent lumps. Simmer gently for 20 minutes, skimming as needed. The velouté is ready when it coats the back of a spoon in a smooth, even film.
2. 2
   Sweat the white mushrooms in butter and lemon juice over low heat, covered, until they yield their liquid. The liquid must remain pale and clear — any browning of the mushrooms or their juice introduces roasted flavours that do not belong in this sauce. Strain the liquid and reserve; discard or use the mushrooms separately.
3. 3
   Add the mushroom cooking liquid, the oyster liquor strained through fine cloth, and the mussel liquor if available to the velouté. Simmer and reduce by one-quarter. The reduction is complete when the sauce deepens slightly in colour and the aroma of the sea becomes pronounced.
4. 4
   This is where the dish lives or dies. Whisk together the egg yolks and heavy cream to form the liaison. Remove the saucepan from the heat. Temper the liaison by adding a ladleful of the hot velouté to it gradually, whisking constantly. Return the tempered mixture to the pan in a slow stream, still whisking. Keep the heat at its lowest if any warmth is needed — the sauce must never approach a simmer from this point forward. Scrambled yolks cannot be recovered.
5. 5
   Off the heat entirely, mount the sauce by whisking in the cold butter, cube by cube, until each piece is fully absorbed and the surface carries a light gloss. The emulsion is achieved when the sauce moves as a single body when the pan is tilted.
6. 6
   Pass the sauce through a fine chinois, pressing gently. The finished Normande should be ivory with a faint golden tinge from the yolks, thick enough to nap a sole fillet without running, and taste of the sea layered with cream, mushroom, and a mineral depth from the oyster liquor.