Blanquette de la Mer — Seafood in White Velouté

Ingredients

• 200 g monkfish, trimmed, cut into portions
• 200 g turbot, cut into portions
• 200 g salmon, cut into portions slightly larger than the white fish
• 8 scallops
• 12 mussels, cleaned, opened à la marinière; liquor strained and reserved
• 8 langoustine tails, shelled
• For the fish fumet
• 1 litre fish fumet, prepared with white wine, shallots, and mushroom trimmings
• For the sauce
• 500 ml poaching liquid, from the fumet; reduced by half
• 200 ml fish velouté
• 100 ml double cream
• For the liaison
• 2 egg yolks, beaten with the cream below
• 50 ml double cream, beaten with the egg yolks
• 1 squeeze lemon juice, added off the heat with the liaison
• For the garniture
• 24 mushroom caps, turned; cooked à blanc in lemon water and butter
• 16 pearl onions, glazed à blanc in butter, water, and sugar without colour
• To finish
• 1 tbsp Noilly Prat, dry vermouth; added to the fumet before reducing
• 1 small bunch chervil, pluches only

Method

1. 1
   Open the mussels à la marinière. Strain their liquor through a fine cloth and add it to the fish fumet. The fumet must remain pale and clear — any cloudiness or colour at this stage will compromise the finished sauce.
2. 2
   Cook the turned mushroom caps à blanc: simmer in lemon water with butter over a moderate heat until just tender. Reserve. Glaze the pearl onions à blanc in butter, water, and a pinch of sugar, allowing the liquid to reduce to a light coating gloss without any browning.
3. 3
   Bring the fish fumet to 80 °C. Add the Noilly Prat. Slide in the monkfish and turbot. Poach gently — the liquid must not boil — for 5 minutes. The flesh should offer slight resistance when pressed; it must not flake freely at this stage.
4. 4
   Add the scallops, langoustine tails, and salmon to the poaching liquid. Continue at 80 °C for a further 3 minutes. The scallops are done when they are just opaque through to the centre and yield to gentle pressure without springing back. Remove all fish and shellfish and keep warm, covered.
5. 5
   Measure 500 ml of the poaching liquid into a wide sauté pan. Reduce by half over a steady heat. Add the 200 ml fish velouté and 100 ml double cream. Reduce to nappant consistency — the sauce coats the back of a spoon and a line drawn through it holds clean. Pass through a fine chinois.
6. 6
   This is where the dish lives or dies. Remove the pan entirely from the heat. Beat the 2 egg yolks with the 50 ml cream and pour into the sauce in a steady stream, stirring constantly. The sauce must not return to a boil; heat alone will curdle the liaison irreversibly. Add the lemon juice, mushrooms, and pearl onions. The finished sauce is fluid silk — uniformly pale, with no streaks or graininess.
7. 7
   Arrange the fish and shellfish in a deep warmed platter. Place the mussels in their half-shells around the edge. Ladle the sauce over the fish, ensuring every piece is coated. Scatter chervil pluches. The surface should be an unbroken pale ivory, with the coral of the salmon and the mussels as the only departures from whiteness.