In the bowl of a food processor, combine the shrimp, salmon chervil, tarragon, egg whites, salt and pepper and puree for 30 seconds to 1 minute. Be sure to scrape down the side of the bowl to ensure you end up with a smooth puree. Add 1 cup cream and pulse until well combined.
Preheat the oven to 300°F.
Remove the puree from the refrigerator and fold in 1 cup of the cream with a spatula or wooden spoon. Using a whisk, beat the remaining heavy cream to medium peaks. Fold the whipped cream into the fish mixture and refrigerate for 30 minutes.
To test the mousseline for seasoning and consistency, bring a small saucepan of salted water to a boil. Drop a small ball (about 2 teaspoons) of the batter into the water, and poach until it rises to the surface. As necessary, add more cream or seasoning.
Brush the insides of twelve 4-ounce ramekins with the butter and divide the mousseline among them. Place the ramekins into deep roasting pan and pour in enough boiling water into the pan to come halfway up the sides of the ramekins. Cover the ramekins with a piece of buttered and bake until firm and puffed, 35 to 40 minutes. Remove and turn each ramekin on its side, and carefully drain any excess cooking liquid.
Invert and unmold onto serving plates, turning them top-side up. Spoon the Tomato Cream Sauce on top of and around the mousselines, and serve.
Yield: 12 appetizer portions
TOMATO CREAM SAUCE:
Heat the oil in a medium saucepan over medium-high heat. Add the onions and cook, stirring, until soft, about 3 minutes. Add the garlic and cook for 30 seconds. Add the tomatoes, thyme and 1/2 teaspoon of the salt, and cook until the tomatoes give up their liquid, about 5 minutes, stirring from time to time. Add the fish broth and tomato paste. Bring to a boil and cook until reduced by 50% in volume. Add the cream and cook until reduced by 50% in volume.
Add the remaining 1/4 teaspoon salt, remaining 2 tablespoons, butter and parsley. Remove the thyme sprigs. With an immersion blender, puree the sauce. Ladle the sauce on top of and around the Mousselines on serving plates.
Yield: a generous 2 cups