A creamy fish casserole is one of those dishes that feels both rustic and elegant. It is hearty enough for a family dinner yet refined enough to serve at a dinner party. The combination of fresh fish, tender vegetables, and a velvety cream sauce creates a comforting meal that celebrates the flavors of the sea. Adding shellfish like mussels or clams makes it even more special, while the potatoes help turn it into a complete one-dish meal.
The key to this dish lies in the sauce. A base of sautéed shallots, carrots, and leeks is enriched with butter, thickened gently with flour, and lifted with fish stock and cream. The fish is added toward the end, simmering just long enough to turn tender without losing its delicate texture. Finished with fresh herbs and served hot, this casserole is a soul-warming comfort food.
Ingredients (serves 4)
1 carrot, sliced
1 leek, white part only, sliced
1 shallot, minced
2 tablespoons butter
1 tablespoon flour
1½ cups fish stock or vegetable broth
½ cup heavy cream
500 to 600 g firm white fish fillets such as cod or haddock, cut into chunks
8 to 10 mussels or clams, optional
½ cup cooked small potatoes or baby potatoes
1 teaspoon Dijon mustard, optional
Fresh parsley or dill, chopped
Salt and pepper to taste
Instructions
Melt the butter in a large skillet or casserole pan over medium heat. Add the shallot, carrot, and leek. Sauté for 5 to 7 minutes until softened but not browned.
Stir in the flour and cook for about 1 minute, stirring constantly. Gradually whisk in the fish stock, a little at a time, to prevent lumps. Simmer gently for 5 to 6 minutes until slightly thickened. Stir in the cream and mustard if using, then season with salt and pepper.
Nestle the fish chunks and mussels or clams into the sauce. Cover and simmer gently for 8 to 10 minutes, or until the fish is cooked through and the shellfish have opened. Discard any that remain closed.
Stir in the cooked potatoes, sprinkle generously with fresh parsley or dill, and serve immediately.
Serving ideas
This creamy fish casserole is perfect with crusty bread, which soaks up the sauce beautifully. It also pairs well with steamed rice, buttered noodles, or even a simple green salad to add freshness. For a more rustic presentation, bring the whole casserole dish to the table and serve family-style.
Variations
Swap the fish for salmon, halibut, or even shrimp for a different flavor.
Add more vegetables like fennel, celery, or peas to enrich the dish.
Replace the cream with coconut milk for a lighter, dairy-free version with a subtle sweetness.
Top with breadcrumbs and cheese, then bake briefly under the broiler for a gratin-style finish.
Tips for success
Use firm fish fillets that hold their shape when cooked. Avoid overcooking, as fish can turn dry and flaky quickly.
If using shellfish, choose fresh mussels or clams and clean them thoroughly before adding.
Prepare the potatoes ahead of time so they can be stirred in at the last moment without delaying the dish.
Storage
Leftovers can be stored in an airtight container in the refrigerator for up to two days. Reheat gently on the stovetop over low heat to avoid overcooking the fish. Freezing is not recommended because the creamy sauce may separate and the texture of the fish can become less pleasant.
Why this recipe works
This dish balances creaminess with freshness. The vegetables provide a sweet base, the stock and cream form a silky sauce, and the fish contributes a clean, delicate flavor. Mussels or clams, if used, add a briny depth that enhances the ocean character of the casserole. The potatoes make it filling while keeping the dish simple and rustic.
Creamy fish casserole is proof that comfort food can also be light and refined. With its delicate balance of flavors and its simple preparation, it is a dish that can easily become a weeknight favorite while still being impressive enough for guests.