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A bubbling hot seafood gratin, freshly baked and golden brown.

Classic Seafood Gratin

This Classic Seafood Gratin features a luscious medley of shrimp, scallops, and flaky white fish baked in a rich, cheesy béchamel sauce, topped with crispy golden breadcrumbs for a comforting and elegant dish.
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Prep Time 25 minutes
Cook Time 30 minutes
Total Time 55 minutes
Servings 4 people
Calories 450 kcal

Equipment

  • Large skillet
  • Dutch oven (optional)
  • Slotted spoon
  • Bowl
  • Whisk
  • Oven-safe gratin dish (9x13 inch baking dish or 2-quart casserole dish)

Ingredients
  

Main Ingredients

  • 1 tablespoon olive oil
  • 1 tablespoon unsalted butter
  • 1 small shallot finely minced
  • 2 garlic cloves minced
  • ¼ cup dry white wine like Sauvignon Blanc or Pinot Grigio
  • 1 lb mixed seafood shrimp, scallops, flaky white fish like cod or haddock, cut into 1-inch pieces
  • Salt to taste
  • Freshly ground black pepper to taste
  • 2 tablespoons all-purpose flour
  • 1 ½ cups whole milk warmed
  • ½ cup heavy cream
  • ½ teaspoon Dijon mustard optional
  • ¼ teaspoon nutmeg freshly grated
  • ½ cup Gruyère cheese shredded, plus more for topping
  • ½ cup Parmesan cheese finely grated, plus more for topping
  • ¼ cup fresh parsley chopped, plus more for garnish
  • ½ cup panko breadcrumbs
  • 2 tablespoons unsalted butter melted

Instructions
 

Preparation

  • Heat olive oil and 1 tablespoon butter in a large skillet over medium heat, then add shallots and cook until softened.
  • Stir in minced garlic and cook for another minute until fragrant.
  • Pour in white wine, scraping up browned bits, and simmer for 1-2 minutes to reduce slightly.

Cooking Seafood

  • Add mixed seafood to the skillet and cook gently for 2-4 minutes until shrimp are pink and scallops are opaque, and fish is mostly cooked.
  • Season lightly with salt and pepper, then remove seafood with a slotted spoon and set aside.

Make Béchamel

  • Melt the remaining 2 tablespoons of butter in the same skillet over medium heat.
  • Whisk in flour and cook for 1 minute, stirring constantly to create a roux.
  • Gradually whisk in warmed milk and heavy cream until smooth and thick, about 5-7 minutes.
  • Stir in Dijon mustard and nutmeg, then season with salt and pepper to taste.
  • Remove from heat, then stir in Gruyère and Parmesan cheeses until melted and smooth, and fold in chopped fresh parsley.

Assemble and Bake

  • Gently add the cooked seafood back into the sauce, stirring carefully to coat.
  • Pour the seafood mixture into an oven-safe gratin dish.
  • Combine panko breadcrumbs, melted butter, a pinch of salt, and a sprinkle of Parmesan or Gruyère cheese in a small bowl.
  • Mix until crumbs are evenly coated, then sprinkle over the seafood mixture.
  • Preheat oven to 375°F (190°C) and bake for 20-25 minutes until bubbling and the topping is golden brown.
  • Let the gratin rest for 5-10 minutes before serving to allow the sauce to set slightly.

Notes

To prevent the seafood from becoming rubbery, be careful not to overcook it in the initial step. The rich béchamel sauce and crispy breadcrumb topping make this a delightful dish for a special occasion or a comforting weeknight meal. You can also experiment with other types of firm white fish.