2 to 3 tablespoons unsalted butter, softened
3 tablespoons finely minced shallot
One 5- to 6-pound sea bass fillet (skin on),
cut into 1 1/2-inch slices - or
One 3-pound sea bass fillet or halibut steak,
cut into slices 3/4 to 1 inch thick
Salt and freshly ground pepper
3 leeks (white part only), cut julienne and blanched
1 1/2 cups dry white wine, preferably Chablis
1 1/2 cups fish fumet *
1 cup whipping cream
2 egg yolks [Egg Safety Information]
Juice of 1/2 lemon
4 tablespoons (1/2 stick) unsalted butter,
cut into 4 pieces
1 tablespoon olive oil
2 tomatoes, peeled, seeded and chopped
4 mushrooms, fluted (garnish)

Preheat oven to 450 degrees F. Select a shallow, heatproof baking dish
just large enough to accommodate fish. Cut waxed or parchment paper
same size as dish. Grease paper and dish with 2 to 3 tablespoons softened butter. Sprinkle dish with shallot. Season fish lightly with salt and pepper
and arrange over shallot. Distribute leeks over and around fish. Add wine
and fumet. Place paper buttered side down over fish. Bring liquid to sim-
mer over direct heat. Transfer dish to oven and bake until fish is slightly
springy to the touch and still underdone (it will continue to cook after
being removed from oven), approximately 20 minutes. Remove from
oven and drain liquid into non-aluminum saucepan. Keep fish warm,
covered with buttered paper and with lid. Reduce liquid over high heat
to about 1 cup. Remove from heat.
Beat cream with yolks and lemon juice. Gradually whisk in 1/2 cup
reduced liquid 1 tablespoon at a time, beating well after each addition.
Whisk back into remaining liquid, place over very low heat and continue whisking until thickened. Remove from heat and whisk in butter 1 piece
at a time, beating in completely after each addition. Cover and keep
warm in bain-marie**.
Heat oil in small skillet over medium-high heat. Add tomatoes and sauté
briefly until just heated through. Pour sauce over fish and garnish each
serving with a spoonful of tomato and fluted mushrooms. Serve
immediately. Serves 4.

* fumet -a concentrated stock
** bain-marie - (water bath) ...placing a container of food in a large,
shallow pan of warm water, which surrounds the food with gentle heat