This classic French dish is famed for its delicacy and always impresses guests which makes it an ideal choice when you're planning your next dinner party.
Place the grapes into a bowl, pour over boiling water and leave for 1 minute. Refresh in cold water and slip off the skins using a small sharp knife and cut in half lengthways. Place into a bowl, cover and chill until needed.
Cut each sole fillet in half lengthways, season well and then roll up tightly keeping the skinned side inside.
Melt a little butter in a large frying pan, place the rolled fillets into the pan with 2 sprigs of tarragon and then pour over the vermouth or wine.
Place the pan over a medium heat and bring up to simmering point, cover and poach for 3-4 minutes.
Transfer the sole to a warm serving dish and cover lightly with foil and place the fish poaching liquid over a high heat a bubble until it has reduced to one third of its volume.
Preheat the grill to high.
Melt butter in a small saucepan, add the plain flour and stir to make a smooth paste. Cook for 2 minutes over a low heat to cook out the flour and then gradually add the reduced poaching liquid, the double cream and milk whisking until it is all incorporated and you have a light sauce the thickness of single cream.
Season with a little salt and black pepper and a squeeze of lemon juice. Loosen with a little warm water if the sauce is too thick.
Pour the sauce over the poached fish, scatter with the prepared grapes and place under the grill for 3-4 minutes or until it is golden brown on top. Scatter with a little more chopped tarragon. Serve 3 sole fillets per person.
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Sole fillets may only be available in limited stores.