Instructions: Place the potato in a large saucepan, add the salt and water to cover, and bring to the boil. Cook the potato for 15 minutes, or until tender, then drain and shake over heat until dry. Crush with a masher or push through a mouli or sieve (it is not advisable to mash them in a food processor). Beat in the milk, then add 1 teaspoon of the wasabi to the potato and season with salt and pepper.

(To keep hot without spoiling, level the surface of the puree in the pan and cover with 3 tbsps of hot milk and a good knob of butter, then seal the pan with a tight-fitting lid.)

Rinse the salmon very lightly and pat dry with absorbent kitchen paper.

Preheat the barbecue or a ribbed grill pan to medium hot, then brush the rack or pan with vegetable oil. When the oil is hot, but not smoking, brush the salmon fillet lightly with vegetable oil and place on the rack or in the pan. Cook for about 6 minutes, turning once. Mix the remaining 1 teaspoon wasabi with first the lime juice, and then the oil, until combined. To serve, spoon the creamed potato onto 4 warm serving plates. Peel away the skin of the salmon steaks and arrange on top. If a char-scored finish is wanted, have ready a few metal skewers made red hot over a flame and use to score the top of the fish. Garnish with the chervil sprigs, if using. Drizzle the wasabi mixture around the edge of each plate. Serve with a green vegetable in season. Editors note: Wasabi is a green horseradish-like condiment. You can buy it in powdered form, and sometimes as a paste, at Asian and specialty markets. If using the powder, reconstitute according to package directions before measuring.

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