Divide the seafood among the 4 gratin dishes. Strew the vegetables on top of each dish. Pour the sauce equally over the seafood and vegetables and spoon the crumbs evenly on top. Bake for 20 minutes, until the top is browned and the sauce is bubbly. Serve hot.
Preheat the oven to 375 degrees F. Place 4 individual gratin dishes on sheet pans. (If recipe is doubled serve it in a 14 by 9 1/4-inch oval gratin dish.) Combine the stock, cream, 1/2 cup of the wine, the tomato puree, and saffron in a medium saucepan. Bring to a boil, lower the heat, and add the shrimp.
1 cup seafood stock or clam juice. 1 cup heavy cream. 1/2 cup plus 3 tablespoons good white wine, such as Chablis, divided. 3 tablespoons tomato puree. 1/2 teaspoon saffron threads. 8 ounces raw shrimp, peeled, deveined, and cut in half crosswise.
Combine the stock, cream, 1/2 cup of the wine, the tomato puree, and saffron in a medium saucepan. Bring to a boil, lower the heat, and add the shrimp. After 3 minutes, use a slotted spoon to remove the shrimp to a bowl. Add the halibut to the stock for 3 minutes, until just cooked through, and remove to the same bowl.