Seafood Gratin Recipe hits that cozy, creamy, cheesy comfort-food spot while still feeling a little fancy, like sweatpants with great jewelry. It works perfectly for date nights, holidays, or a weeknight treat, and you can get it on the table in about 50 minutes total. I first made a version of this in a tiny apartment kitchen with one sad pan, so if I pulled it off there, you absolutely can too.

Why Make This Seafood Gratin Recipe at Home

You control the seafood quality, the amount of cream, and the level of cheesiness, so the flavor stays rich and luxurious without feeling heavy. Restaurant seafood gratin often costs a lot, yet it usually skimps on actual seafood, while a homemade version lets you pack in shrimp, scallops, and fish.

You also customize it for picky eaters or allergies, swap in what you find on sale, and bake it in whatever dish you own. Leftovers reheat beautifully, so you cook once and enjoy it again the next day with almost no effort.

“This Seafood Gratin Recipe tastes like a cozy seafood casserole from a great coastal bistro, but you pull it out of your own oven. ★★★★★”

Ingredients You Need

Seafood

8 ounces raw shrimp, peeled and deveined
- Medium or large work best so they do not overcook too fast.
8 ounces sea scallops
- If scallops look huge, cut them in half horizontally.
8 ounces firm white fish, cut in 1-inch chunks
- Cod, haddock, halibut, or pollock all hold up well.
Optional: 4 ounces lump crab meat
- Use pasteurized refrigerated crab if fresh crab costs too much.

Aromatics and flavor base

2 tablespoons unsalted butter
1 tablespoon olive oil
1 small yellow onion, finely diced
2 cloves garlic, minced
1 small leek, white and light green parts only, thinly sliced and rinsed
- If you skip leeks, add another half onion.
1 teaspoon kosher salt, plus more to taste
½ teaspoon freshly ground black pepper
½ teaspoon sweet paprika
¼ teaspoon smoked paprika
- Smoked paprika adds a subtle “from the coast” vibe without actual smoke.

Creamy sauce

2 tablespoons all-purpose flour
1 cup seafood stock or low-sodium chicken broth
- Pantry shortcut: use Better Than Bouillon or a good quality stock cube with water.
1 cup heavy cream
- You can swap half-and-half, but the sauce turns slightly thinner.
1 teaspoon Dijon mustard
1 teaspoon fresh lemon zest
1 tablespoon fresh lemon juice
2 tablespoons chopped fresh parsley
1 tablespoon chopped fresh chives or green onion tops

Cheese and topping

1 cup grated Gruyère cheese
- You can use Swiss cheese if Gruyère costs too much.
½ cup grated Parmesan cheese
1 cup panko breadcrumbs
- Regular breadcrumbs also work, but panko gives a better crunch.
2 tablespoons melted butter
Pinch of salt and pepper

Optional flavor boosters

⅛ teaspoon cayenne pepper for gentle heat
1 teaspoon Old Bay seasoning for a classic seafood flavor
Extra lemon wedges for serving

Equipment

10 to 12 inch oven-safe skillet or a medium saucepan
2 to 2½ quart baking dish (or 4 individual gratin dishes / ramekins)
Cutting board and sharp knife
Whisk
Mixing bowl for breadcrumb topping
Measuring cups and spoons

Tips & Mistakes

Use dry seafood, not waterlogged, so the sauce stays thick and creamy.
Pat shrimp, scallops, and fish very dry with paper towels before cooking.
Cut seafood in similar sizes so everything cooks at the same rate.
Avoid tiny shrimp, which turn rubbery before the sauce finishes bubbling.
Do not boil the cream sauce; simmer it gently so it stays silky.
Add cheese off the heat so it melts smoothly and does not turn grainy.
Season the sauce slightly more than you think you need; the breadcrumbs mute salt a bit.
Taste the sauce before you add seafood and adjust salt, pepper, and lemon.
Toast the breadcrumb topping lightly in the pan or with melted butter so it bakes golden, not pale.
Spread the seafood in a single layer in the baking dish so it cooks evenly.
Avoid overbaking; pull the gratin when the sauce bubbles around the edges and the topping turns deep golden.
Let the gratin rest 5 to 10 minutes so the sauce thickens and does not run all over the plate.

How to Make Seafood Gratin Recipe

Step 1: Prep the seafood and oven

Heat the oven to 400°F (200°C).
Pat shrimp, scallops, and fish very dry with paper towels and place them in a bowl.
Sprinkle with a pinch of salt, pepper, and a little lemon juice, then set aside while you start the sauce.

Step 2: Cook the aromatics

Heat a large skillet over medium heat and add butter and olive oil.
Add onion and leek, then cook until they turn soft and lightly golden, about 5 to 7 minutes.
Stir in garlic, paprika, and any optional Old Bay or cayenne, then cook 30 seconds until fragrant.

Step 3: Make the creamy base

Sprinkle flour over the vegetables and stir until the flour coats everything and no dry spots remain.
Cook this mixture 1 to 2 minutes to remove the raw flour taste.
Slowly whisk in seafood stock, a little at a time, until the mixture turns smooth.

Step 4: Add cream and flavor

Pour in the cream and whisk until the sauce looks smooth and slightly thick.
Stir in Dijon mustard, lemon zest, lemon juice, salt, and pepper.
Let the sauce simmer gently for 3 to 5 minutes until it coats the back of a spoon.

Step 5: Add cheese and herbs

Turn off the heat.
Stir in Gruyère and half of the Parmesan until the cheese melts into the sauce.
Add parsley and chives, then taste and adjust seasoning with more salt, pepper, or lemon.

Step 6: Combine seafood with the sauce

Add shrimp, scallops, fish, and optional crab to the skillet.
Gently fold the seafood into the sauce so you do not break up the fish pieces.
Transfer everything to the baking dish, spreading the seafood in an even layer.

Step 7: Mix the crunchy topping

In a bowl, combine panko, remaining Parmesan, melted butter, a pinch of salt, and pepper.
Toss until the breadcrumbs soak up the butter and look evenly coated.
Sprinkle the mixture evenly over the seafood and sauce.

Step 8: Bake the gratin

Place the baking dish on a sheet pan to catch any bubbling sauce.
Bake 18 to 22 minutes, until the topping looks deep golden and the sauce bubbles around the edges.
If the topping needs more color, switch the oven to broil for 1 to 2 minutes and watch closely.

Step 9: Rest and serve

Remove the gratin from the oven and let it rest 5 to 10 minutes.
Sprinkle with extra parsley or chives.
Serve hot with lemon wedges on the side so everyone can add brightness to taste.

Variations I've Tried

I swap the white fish for salmon chunks and keep the rest of the recipe the same for a richer version. I also make a “shrimp only” gratin when shrimp goes on sale and it still tastes luxurious. Sometimes I stir in blanched spinach or kale into the sauce for extra greens.

I also tried a lighter version with half-and-half and a bit more stock, plus a thinner layer of cheese, and it still tasted comforting but less heavy. You can also use a mix of mozzarella and Parmesan if you want more stretch and less nutty flavor. If you like a little heat, add extra cayenne or a pinch of crushed red pepper to the sauce.

How to Serve Seafood Gratin Recipe

Serve this Seafood Gratin Recipe with a simple green salad and a bright vinaigrette to cut through the richness. Crusty bread, garlic bread, or toasted baguette slices work perfectly to scoop up every bit of the creamy sauce. You can also spoon it over plain rice, buttered noodles, or mashed potatoes for a full comfort-food plate.

If you cook for kids or picky eaters, pair it with steamed broccoli, green beans, or roasted carrots. Add lemon wedges on the side so everyone can adjust the brightness exactly how they like it.

How to store

Cool leftovers to room temperature within 1 hour, then cover the dish tightly or transfer to airtight containers.
Store in the fridge for up to 3 days.
Freeze portions in freezer-safe containers for up to 2 months; thaw overnight in the fridge before reheating.
Reheat in a 350°F (175°C) oven, covered with foil, for 15 to 20 minutes until hot, then uncover for a few minutes to crisp the topping again.
You can also reheat small portions in the microwave in short bursts, but use the oven at the end for a quick crisp on top if you want the best texture.