Seafood au Gratin is a luxurious French-inspired seafood casserole featuring tender shrimp, scallops, crab meat, and white fish baked in a rich, creamy cheese sauce and topped with a golden, crispy Parmesan breadcrumb crust. The combination of delicate seafood, velvety béchamel sauce, aromatic herbs, and bubbling cheese creates an elegant dish that's perfect for family dinners, holiday celebrations, or entertaining guests.

This comforting recipe pairs beautifully with crusty bread, buttered rice, roasted vegetables, or a fresh green salad, making it a complete and satisfying meal.

Why You'll Love This Recipe

  • Rich, creamy, and comforting
  • Loaded with tender mixed seafood
  • Golden, crispy cheese topping
  • Restaurant-quality dish made at home
  • Perfect for holidays and special occasions
  • Easy to customize with your favorite seafood
  • Ready in about one hour
  • Excellent make-ahead option

What is Seafood au Gratin?

Au Gratin is a French cooking technique in which a dish is topped with cheese, breadcrumbs, or both, then baked until the topping becomes golden brown and crisp.

In Seafood au Gratin, a medley of seafood is coated in a creamy béchamel sauce enriched with cheese, transferred to a baking dish, topped with seasoned breadcrumbs and Parmesan, and baked until bubbling and beautifully browned.

Typical seafood includes:

  • Shrimp
  • Scallops
  • Crab meat
  • White fish
  • Lobster (optional)
  • Mussels (optional)

The result is a creamy seafood bake with a crisp, flavorful crust.

Ingredients

For the Seafood

  • 300 g (10 oz) shrimp, peeled and deveined
  • 250 g (9 oz) sea scallops
  • 300 g (10 oz) firm white fish (cod, haddock, halibut, or pollock), cut into bite-sized pieces
  • 200 g (7 oz) lump crab meat, checked for shells
  • 1 tablespoon fresh lemon juice
  • Salt and freshly ground black pepper, to taste

Creamy Cheese Sauce

  • 3 tablespoons unsalted butter
  • 2 tablespoons extra virgin olive oil
  • 1 small onion, finely diced
  • 3 garlic cloves, minced
  • 3 tablespoons all-purpose flour
  • 2 cups whole milk
  • ½ cup heavy cream
  • 1 cup shredded Gruyère cheese
  • ½ cup grated Parmesan cheese
  • 1 teaspoon Dijon mustard
  • ½ teaspoon smoked paprika
  • 1 teaspoon fresh thyme leaves
  • 2 tablespoons chopped fresh parsley
  • ½ teaspoon sea salt
  • ½ teaspoon freshly ground black pepper

Au Gratin Topping

  • 1 cup panko breadcrumbs
  • ½ cup grated Parmesan cheese
  • 2 tablespoons melted butter
  • 1 tablespoon chopped parsley
  • ½ teaspoon garlic powder
  • ½ teaspoon paprika

Garnish

  • Fresh parsley
  • Chopped chives
  • Lemon wedges
  • Freshly cracked black pepper

Kitchen Equipment

  • 9 × 13-inch baking dish
  • Large skillet or saucepan
  • Whisk
  • Mixing bowls
  • Wooden spoon
  • Measuring cups and spoons

Preparation Time

  • Prep Time: 20 minutes
  • Cook Time: 35 minutes
  • Total Time: 55 minutes

Serves: 6

Step 1: Prepare the Seafood

Pat the seafood dry with paper towels.

Lightly season with:

  • Salt
  • Black pepper
  • Lemon juice

Set aside while preparing the sauce.

Step 2: Make the Cheese Sauce

Preheat the oven to 190°C (375°F).

In a large skillet, melt the butter with the olive oil over medium heat.

Add the onion and cook for 5–6 minutes, until softened.

Stir in the garlic and cook for 30 seconds until fragrant.

Sprinkle the flour over the vegetables and whisk continuously for 1–2 minutes to create a smooth roux.

Gradually whisk in the milk until smooth.

Add the heavy cream and simmer gently for 3–5 minutes, stirring frequently, until slightly thickened.

Stir in:

  • Gruyère cheese
  • Parmesan cheese
  • Dijon mustard
  • Smoked paprika
  • Thyme
  • Parsley
  • Salt
  • Black pepper

Continue stirring until the cheese has melted and the sauce is smooth.

Step 3: Assemble the Casserole

Lightly grease the baking dish.

Arrange the seafood evenly in the dish.

Pour the warm cheese sauce over the seafood, ensuring everything is well coated.

Step 4: Prepare the Topping

In a bowl, combine:

  • Panko breadcrumbs
  • Parmesan cheese
  • Melted butter
  • Parsley
  • Garlic powder
  • Paprika

Mix until evenly coated.

Sprinkle the topping evenly over the casserole.

Step 5: Bake

Bake uncovered for 25–30 minutes, or until:

  • The seafood is cooked through.
  • The sauce is bubbling.
  • The topping is golden brown and crisp.

For a deeper golden finish, broil for the final 1–2 minutes, watching carefully to prevent burning.

Step 6: Rest

Allow the casserole to rest for 5 minutes before serving to help the sauce thicken slightly.

Step 7: Serve

Garnish with:

  • Fresh parsley
  • Chopped chives
  • Lemon wedges
  • Freshly cracked black pepper

Serve hot with your favorite side dishes.

Flavor Profile

This Seafood au Gratin offers:

  • Tender, juicy seafood
  • Rich, creamy cheese sauce
  • Nutty Gruyère and Parmesan
  • Mild garlic and onion
  • Crispy golden breadcrumb topping
  • Fresh herbs
  • Bright citrus finish

Best Side Dishes

Pair Seafood au Gratin with:

  • Crusty artisan bread
  • Garlic bread
  • Buttered rice
  • Lemon herb rice
  • Mashed potatoes
  • Roasted baby potatoes
  • Steamed asparagus
  • Green beans
  • Caesar salad
  • Mixed Mediterranean salad

Tips for Perfect Seafood au Gratin

Use Fresh Seafood

Fresh seafood provides the best flavor and texture. If using frozen seafood, thaw it completely and pat it dry before cooking.

Don't Overcook the Seafood

The seafood continues cooking in the oven. Baking just until the fish flakes and the shrimp turn opaque keeps everything tender.

Freshly Grate the Cheese

Freshly grated Gruyère and Parmesan melt more smoothly and deliver better flavor than pre-shredded cheese.

Make a Smooth Béchamel

Whisk constantly while adding the milk to avoid lumps and create a silky sauce.

Let It Rest

A brief resting period allows the sauce to set, making the casserole easier to serve.

Delicious Variations

Lobster Seafood au Gratin

Add chunks of cooked lobster meat for an extra luxurious version.

Mediterranean Seafood au Gratin

Mix in chopped spinach, roasted red peppers, olives, artichoke hearts, and crumbled feta cheese before baking.

Spicy Seafood au Gratin

Add cayenne pepper, crushed red pepper flakes, or diced jalapeños to the sauce for a gentle heat.

Mushroom Seafood au Gratin

Sauté sliced mushrooms with the onions for additional earthy flavor.

Gluten-Free Version

Use a gluten-free flour blend for the sauce and gluten-free breadcrumbs for the topping.

Storage

Store leftovers in an airtight container in the refrigerator for up to 2 days.

Freezing is not recommended, as the cream sauce may separate and the seafood can lose its delicate texture.

Reheating

Reheat in a 170°C (340°F) oven for 15–20 minutes, loosely covered with foil.

Avoid overheating to keep the seafood tender.

Nutrition (Approximate Per Serving)

  • Calories: 540
  • Protein: 38 g
  • Fat: 34 g
  • Carbohydrates: 19 g
  • Fiber: 1 g
  • Sugar: 4 g
  • Sodium: 760 mg

Nutritional values are approximate and will vary depending on the ingredients used.

Frequently Asked Questions

Can I use frozen seafood?

Yes. Thaw it completely in the refrigerator and pat it dry thoroughly before adding it to the casserole to prevent excess moisture.

What cheeses work best?

Gruyère and Parmesan provide a classic combination, but Fontina, Swiss, mozzarella, or sharp white cheddar can also be used.

Can I prepare Seafood au Gratin ahead of time?

Yes. Assemble the casserole up to 24 hours in advance, cover, and refrigerate. Add the breadcrumb topping just before baking.

What fish is best for this recipe?

Firm white fish such as cod, halibut, haddock, pollock, or sea bass work well because they hold their shape during baking.

How do I know when it's fully cooked?

The fish should flake easily with a fork, shrimp should be pink and opaque, scallops should be firm yet tender, and the sauce should be bubbling around the edges.

Final Thoughts

Seafood au Gratin is an elegant, creamy baked seafood dish that combines tender seafood with a rich cheese sauce and a crisp golden Parmesan topping. The balance of delicate seafood, velvety béchamel, aromatic herbs, and bubbling cheese makes it an impressive centerpiece for both everyday dinners and festive celebrations. Serve it with crusty bread, rice, or roasted vegetables for a comforting, restaurant-quality meal that's sure to delight every seafood lover.