Seafood Gratin Recipe tastes rich, creamy, and cheesy with tender bites of shrimp, scallops, and flaky white fish tucked under a golden breadcrumb crust. It works perfectly for date night, holidays, or a cozy weeknight, and you can get it on the table in about 50 minutes. I first made a version of this in a tiny apartment kitchen with one pan and a dream of eating like I lived on the coast.

Why Make This Seafood Gratin Recipe at Home

You control the seafood quality, the amount of cream, and the level of cheese, so the dish tastes fresher than most restaurant versions. You also skip the heavy price tag and still get a luxurious, special-occasion feel.

You can prep the seafood gratin ahead, chill it, and bake it right before serving, which saves your sanity on busy nights or holidays. The recipe also works nicely for small households, since leftovers reheat well and taste even better the next day.

“This seafood gratin recipe tastes like a fancy coastal restaurant dinner that you secretly made in yoga pants at home. ★★★★★”

Ingredients You Need

Seafood

8 ounces shrimp, peeled and deveined
- Medium or large shrimp work best so they stay juicy.
8 ounces sea scallops
- If scallops look large, cut them in half so they cook evenly.
8 ounces firm white fish, cut in 1 inch chunks
- Cod, haddock, halibut, or pollock all work.
4 ounces lump crab meat, drained
- Canned or refrigerated crab both work; choose the best quality your budget allows.

You can use frozen seafood as a shortcut. Thaw it in the fridge overnight and pat it very dry so the sauce does not water down.

Aromatics and Flavor Base

3 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
- You can skip the leek and add extra onion if you want a pantry version.
1 teaspoon kosher salt, plus more to taste
½ teaspoon black pepper
½ teaspoon smoked paprika or sweet paprika
¼ teaspoon crushed red pepper flakes
- Optional, but it adds a gentle heat that balances the cream.

Sauce

3 tablespoons all purpose flour
1 cup seafood stock or low sodium chicken broth
- You can use vegetable broth in a pinch.
1 cup whole milk
½ cup heavy cream
- You can swap half and half for a lighter version, but the sauce will taste slightly less rich.
1 teaspoon Dijon mustard
1 teaspoon lemon zest
2 tablespoons fresh lemon juice
2 tablespoons chopped fresh parsley
1 tablespoon chopped fresh chives or green onion tops

Cheese and Topping

1 cup grated Gruyere cheese
- You can use Swiss cheese or a blend of Swiss and mozzarella if you cannot find Gruyere.
½ cup grated Parmesan cheese
1 cup panko breadcrumbs
- Regular breadcrumbs also work, but panko gives a lighter, crunchier top.
2 tablespoons melted butter
1 tablespoon olive oil
1 teaspoon garlic powder
½ teaspoon dried thyme or Italian seasoning

Optional Add Ins

1 cup small cooked potatoes, cut in chunks
1 cup blanched broccoli florets or peas
Extra lemon wedges for serving

Equipment

10 to 12 inch oven safe skillet or a 2 quart baking dish
Medium saucepan
Cutting board and sharp knife
Whisk
Mixing bowls
Measuring cups and spoons

Tips & Mistakes

Pat all seafood very dry so the gratin sauce stays thick and creamy instead of watery.
Cut fish and scallops into similar size pieces so everything cooks at the same speed.
Use room temperature milk and cream to help the sauce thicken smoothly and avoid lumps.
Whisk the flour into the fat and cook it for at least 1 minute so the gratin does not taste like raw flour.
Add the broth and milk slowly while you whisk so the sauce stays silky and smooth.
Season the sauce well before you add the seafood, since bland sauce leads to bland gratin.
Do not overbake, or the seafood will turn rubbery; pull it when the top browns and the sauce bubbles around the edges.
Broil only for a minute or two at the end and watch closely so the breadcrumb topping does not burn.
Use a shallow baking dish so the topping browns nicely and the sauce heats evenly.
Let the seafood gratin rest for 5 to 10 minutes before serving so the sauce thickens slightly and does not run all over the plate.

How to Make Seafood Gratin Recipe

Step 1: Prep the Seafood

Pat the shrimp, scallops, and fish pieces very dry with paper towels. Pick through the crab meat and remove any bits of shell. Season all the seafood lightly with salt and pepper, then set it aside in the fridge while you make the sauce.

Step 2: Sauté the Aromatics

Heat 3 tablespoons butter and 1 tablespoon olive oil in a medium saucepan over medium heat. Add the diced onion and sliced leek, then cook until they turn soft and translucent, about 5 to 7 minutes. Stir in the minced garlic, smoked paprika, crushed red pepper flakes, and a pinch of salt, and cook 1 more minute so the garlic softens and the spices bloom.

Step 3: Make the Roux

Sprinkle the flour over the onion mixture and stir until the flour coats everything and no dry spots remain. Cook this mixture for 1 to 2 minutes, stirring often, so the flour loses its raw taste and turns slightly golden. Keep the heat at medium so the roux does not scorch.

Step 4: Build the Creamy Sauce

Slowly pour in the seafood stock while you whisk constantly, and scrape the bottom of the pan to pick up any browned bits. Add the milk in a slow stream while you keep whisking until the mixture looks smooth. Let the sauce come up to a gentle simmer and cook for 3 to 5 minutes, stirring often, until it thickens enough to coat the back of a spoon.

Pour in the heavy cream and whisk again, then add Dijon mustard, lemon zest, lemon juice, salt, and black pepper. Stir in the chopped parsley and chives. Taste the sauce and adjust the seasoning so it tastes slightly more seasoned than you think you need, since the seafood will mellow it out.

Step 5: Add Cheese and Seafood

Turn off the heat and stir in the Gruyere and half of the Parmesan until they melt into the sauce. Gently fold in the shrimp, scallops, fish, and crab meat so you coat everything without breaking up the fish too much. If you use cooked potatoes or blanched vegetables, fold them in now as well.

Step 6: Transfer to Baking Dish

Lightly grease your oven safe skillet or baking dish with a bit of butter or oil. Pour the seafood mixture into the dish and spread it into an even layer. Preheat your oven to 400°F while you prepare the topping.

Step 7: Mix the Topping

In a bowl, combine panko breadcrumbs, the remaining Parmesan, garlic powder, dried thyme, melted butter, and olive oil. Toss until the crumbs look evenly coated and slightly glossy. Sprinkle this mixture evenly over the top of the seafood mixture.

Step 8: Bake

Place the dish on a baking sheet to catch any drips. Bake at 400°F for 18 to 22 minutes, until the sauce bubbles around the edges and the topping looks golden brown. If the top needs extra color, switch the oven to broil and toast the top for 1 to 2 minutes, watching it closely.

Step 9: Rest and Serve

Remove the seafood gratin from the oven and let it rest for 5 to 10 minutes. This short rest helps the sauce settle and thicken slightly. Sprinkle extra parsley or chives on top, then serve hot.

Variations I’ve Tried

I swap in all shrimp or all scallops when I catch a good sale, and the recipe still works perfectly. I also tried a lighter version with half and half instead of heavy cream and a bit less cheese, and it tasted great for weeknights. Sometimes I add blanched broccoli, peas, or spinach to sneak in more vegetables and stretch the seafood.

I also tested a spicy version with extra crushed red pepper and a pinch of cayenne, which gave the gratin a gentle kick. A cheddar and Monterey Jack blend works if you want a more familiar, melty cheese flavor. You can also use individual ramekins for mini seafood gratins, which look fancy and help with portion control.

How to Serve Seafood Gratin Recipe

Serve seafood gratin recipe hot with a simple green salad and a bright lemony dressing to cut through the richness. Spoon it over fluffy white rice, buttered noodles, or crusty bread so you catch every bit of the creamy sauce. Steamed green beans, roasted asparagus, or sautéed zucchini pair nicely and keep the plate balanced.

You can also portion it into small bowls as an appetizer for a special meal. Add lemon wedges on the side so everyone can squeeze a bit of freshness over the top.

How to store

Cool leftovers to room temperature within 1 hour, then cover the dish tightly or transfer to airtight containers and refrigerate for up to 2 days.
Freeze portions in freezer safe containers for up to 2 months, and label them with the date so you keep track.
Reheat in a 350°F oven, covered with foil, for 15 to 20 minutes until hot and bubbly, then uncover for a few minutes to crisp the topping again.
You can also reheat small portions in the microwave at 50 percent power in short bursts, but the oven keeps the texture better.