In the bowl of a food processor, combine the shrimp, salmon, tarragon, shallots, 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. Refrigerate for at least 30 minutes.

Preheat the oven to 300 degrees 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 12 (4-ounce) ramekins with the butter and divide the mousseline evenly 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 parchment paper 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.

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 percent in volume. Add the cream and cook until reduced by 50 percent 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: Makes a generous 2 cups