Seafood Casserole Recipe

Preheat the oven to 375°F (190°C). Lightly butter or oil a 9x9-inch (or equivalent) baking dish.

If shrimp are large, cut into 1-inch pieces to match the fish. Pat all seafood dry with paper towels and season lightly with 1/4 tsp salt and a pinch of pepper.

Place the seafood in a bowl, toss gently with lemon juice and lemon zest, and set aside while you prepare the sauce (this allows flavors to marry without overcooking).

In a large skillet over medium heat, melt 2 tablespoons butter with 1 tablespoon olive oil. Add the diced onion, celery, and carrot and sauté until softened and translucent, about 6–8 minutes.

Add the minced garlic and thyme and cook 30–45 seconds until fragrant, stirring so garlic does not brown. Stir in the chopped parsley and cook 15 seconds more.

Reduce heat to medium-low. Sprinkle the 3 tablespoons of flour over the softened vegetables and cook, stirring constantly, 1–2 minutes to cook the raw flour taste (do not let it brown).

Gradually whisk in the 1/2 cup white wine, scraping up any brown bits, and let it reduce by half, about 1–2 minutes.

Slowly whisk in the 1 cup stock, 3/4 cup milk, and 1/4 cup half-and-half or cream. Increase heat to medium and bring to a gentle simmer, whisking, until the sauce thickens enough to coat the back of a spoon, 3–5 minutes.

Stir in the Dijon mustard, Worcestershire sauce, Old Bay, remaining 3/4 tsp kosher salt (adjust to taste), 1/2 tsp black pepper, and the remaining lemon zest if desired. Taste and adjust seasoning. If sauce is too thick, stir in up to 2 tablespoons more stock or milk.

Remove the sauce from heat. If using shredded cheese, stir in 1/2 cup shredded Gruyère or cheddar now until melted and incorporated.

Gently fold the prepared shrimp, fish pieces, scallops, and crab meat into the warm sauce until evenly distributed. Be careful not to break up the crab lumps.

Transfer the seafood mixture to the prepared baking dish and spread into an even layer.

In a small bowl, combine the panko, grated Parmesan, and the 2 tablespoons melted butter. Toss until the crumbs are evenly moistened and clump slightly. Sprinkle the breadcrumb mixture evenly over the top of the casserole.

Place the casserole in the preheated oven and bake until the top is golden and bubbling around the edges and the internal temperature of the seafood reaches 145°F (63°C), about 20–25 minutes. If the top browns too quickly, tent loosely with foil for the last 10 minutes.

For a deeper golden crust, broil on high for 1–2 minutes at the end — watch closely to prevent burning.

Remove the casserole from the oven and let rest 5–7 minutes. Sprinkle chopped chives or extra parsley over the top before serving.

Serve warm with lemon wedges on the side and optional crusty bread or steamed rice.