Filets de Soles Bonne Femme (Fillets of Sole with Mushroom and Wine Sauce)

3/4 lb (700 g) fresh mushrooms
4 Tbs butter
2 Tbs vegetable oil
1 Tbs finely chopped shallots or scallions
1 tsp lemon juice
3 lbs (1350 g) grey or lemon sole, or flounder fillets, skinned and cut into uniform serving size
Salt and freshly ground black pepper to taste
3/4 cup dry white wine
Water

For the cream sauce:
4 Tbs butter
4 Tbs flour
3/4 cup heavy cream
1 Tbs lemon juice
1 tsp salt
White pepper to taste

Remove the caps from 12 to 16 of the mushrooms, and slice the resulting stems and the rest of the mushrooms. Melt 2 tablespoons of the butter in a skillet over moderate heat and saute the mushroom caps for 1 or 2 minutes until lightly browned. Set the mushrooms aside. Melt 2 more tablespoons of butter and saute the sliced mushrooms for 2 minutes. Add the shallots or scallions and saute an additional minute. Stir in the lemon juice and set aside. Butter a shallow baking dish and lay the fillets side-by-side, in a single layer. Season the fillets with salt and pepper and spoon the chopped mushroom mixture on top. Pour in the wine and enough water to barely cover the top of the fillets. Cook in a preheated 350F (180C) oven for 10 to 15 minutes or until the fillets are firm to the touch. Remove from the oven and draw up all the liquid with a bulb baster. Strain the liquid into a 2 quart (2 L) saucepan and set the baking dish aside, lightly covered to keep the fish warm. Boil the poaching liquid over high heat until reduced to 1 cup.

In another 2 quart (2 L) saucepan melt 4 tablespoons of butter over moderate heat and stir in the flour. Continue stirring for 2 to 3 minutes. Add the reduced poaching liquid, stirring constantly with a wire whisk until the sauce boils and is very thick. Add the cream and stir, remove from heat and add the lemon juice and season to taste with salt and white pepper. Just before serving, reheat the mushroom caps. Place the fillets on a warm serving platter, spoon the sauce over them, and decorate with the mushroom caps. Serves 6 to 8.