Ask your fishmonger to fillet sole; keep heads, bones and trimmings for stock. Season fillets generously with salt and freshly-ground black pepper and put them in the bottom of a buttered earthenware baking dish. Sprinkle with finely-chopped shallots and mushrooms and add
Arrange poached fillets on a heated serving dish; put fish liquor into a small saucepan; add remaining dry white wine and reduce over a brisk flame to two-thirds of the original quantity. Thicken the sauce if necessary with a beurre manié (made by kneading equal quantities of butter and flour to a smooth paste). Bring sauce to the boil and cook until it has the consistency of cream.
Place 3 mushroom caps on each portion of sole; pour sauce over and glaze for a minute or two under grill before serving.