1Heat the oil and butter in a medium saucepan over medium-high heat. Add the leek, fennel, and garlic; cook, stirring, until the vegetables are softened, about 6 minutes. Add the flour; cook, stirring, 6 to 7 minutes. Whisk in the stock. Bring to a boil. Stir in the tomatoes. Reduce heat to medium-low. Add the lobster, shrimp, scallops, bass, and halibut; cook 5 minutes. Season with salt and pepper. Stir in the parsley. Let cool.
2Preheat the oven to 400°F. Roll out the dough on a lightly floured surface to a 10-inch square, about 1/4 inch thick. Cut out a small vent in the center. Transfer the stew to an 8-inch-square baking dish. Cover with the dough, allowing excess to overhang. Transfer to the freezer until cold, 20 minutes.
