For the Fish:
2 pounds boneless and skinless Turbot filets, cut into 6 portions
1 tablespoon softened butter
¼ cup Fish Fumet (see recipe) made with brut champagne or dry white wine
Juice of ½ lemon
Salt and freshly ground white pepper to taste
For the Champagne Sauce
For the garnish:
8 pinches sea salt
4 sprigs fresh chervil
Preheat the oven to 350°F.
To prepare the fish: Cut each fillet into 6 even pieces. Lightly butter a large cookie sheet with a rim and arrange the fish on the sheet, skin side down. Sprinkle the fillets with the Fish Fumet and lemon juice and season with salt and pepper. Cover with aluminum foil and transfer to the oven. After about 8 minutes, lift the foil and check on the fish; it is done when it is no longer translucent (depending on the thickness of the fish, this may take 10 or 12 minutes). Remove the baking sheet from the oven and set aside in a warm place (on the stovetop or in a 150°F oven) until ready to serve.
To prepare the champagne sauce: Stir together the cream and Fish Fumet in a small saucepan and set over medium-high heat. Reduce the mixture by half, until about 1 cup remains. Spoon half of the broth from the baking sheet containing the cooked fish and strain into the sauce. Add both types of caviar and the chives. Season with salt and pepper and stir well to thoroughly incorporate.
To serve: Place 3 pieces of fish in the center of each warm serving plate. Spoon the sauce over the fish and garnish with a pinch of sea salt and the chervil.