Instructions: To make the fish veloute, in a wide shallow saucepan, gently saute the shallots in butter for about 12 minutes until very soft, yet still uncoloured. Deglaze the pan with the vermouth then boil the liquid for about 10 minutes, or until it has reduced to the consistency of a thin syrup. Stir in the fish stock and bring the liquid to the boil then continue to boil it down until it reduces by about a half. Stir in both the creams, return the pan back to the boil and simnmer the sauce for about 15 minutes or until it acquires a coating consistency. For an extra smooth, velvety texture, pour the sauce through a fine sieve. Set aside, keeping it warm.

Pick the thick stalks off the watercress and discard, then wash the leaves in 2 or 3 changes of cold water. Bring a pan of salted water to the boil and blanch the watercress for 3-4 minutes, then drain and squeeze lightly in a cloth to dry.

In a food processor or liquidizer, blend the watercress to a smooth, fine puree adding a little of the fish veloute to loosen the mixture if necessary. Bring the fish veloute to the boil, then stir in the watercress puree. Pass this sauce through a sieve, rubbing with the back of a ladle, then set aside.

Blanch the homemade tagliatelle in boiling salted water for barely 1 minute then drain. Plunge into very cold water to refresh and drain again. If using ready made, follow the pack instructions.

Open the oysters, remove the flesh from the shell and reserve their juices into a small pan. Discard the flat shells. Scrub the rounded shells clean and pat dry. Spoon 5 small rounds of rock salt onto each plate and sit an oyster shell on each. Reheat the tagliatelle in a little water with the butter. Curl a little of the prepared tagliatelle into each cleaned oyster shell. Keep warm.

Poach the oysters in their own juice cooking for about 2 minutes then remove them from the juice with a slotted spoon and place on the pasta.

Reheat the sauce until just boiling, check the seasoning and spoon over the oysters. Garnish with sprigs of chervil and serve.

Warning: The consumption of raw or partially cooked oysters carries a risk of food poisoning, particularly for pregnant women, children, the elderly and immuno-suppressed.

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