Step 1: Cook the Pasta Shells

1. Bring a large pot of salted water to a boil.
2. Cook the pasta shells according to the package instructions for baked shells (typically 3 minutes less than fully cooked).
3. Transfer shells to a bowl of cold water to stop cooking, then drain and lightly drizzle with olive oil to prevent sticking.

Step 2: Prepare the Seafood Filling

1. Fill a bowl with ice water.
2. Bring the pasta water to a simmer and poach the shrimp for 1–2 minutes until just cooked.
3. Transfer shrimp to the ice bath, then drain and chop into small pieces.
4. In a large bowl, combine the shrimp, crabmeat, and scallops.
5. Add Dijon mustard, mayonnaise, Old Bay seasoning, shallots, and parsley.
6. Season with salt and pepper and mix well.

Step 3: Make the Béchamel Sauce

1. In a saucepan, melt 1 ½ tbsp butter over medium-high heat.
2. Whisk in flour to form a smooth paste and cook for 1 minute.
3. Gradually whisk in milk, stirring constantly to prevent lumps.
4. Add the bay leaf and let the sauce thicken over low heat for about 3 minutes.
5. Remove from heat, discard the bay leaf, and season with salt and pepper.

Step 4: Assemble the Stuffed Shells

1. Lightly grease a 9×13-inch baking dish with olive oil.
2. Spread ½ cup béchamel sauce evenly across the bottom of the dish.
3. Fill each shell with a generous scoop of the seafood mixture.
4. Arrange the stuffed shells snugly in the baking dish.
5. Spoon the remaining béchamel sauce over the shells.

Step 5: Prepare the Breadcrumb Topping

1. Melt the remaining 2 tbsp butter in a small bowl.
2. Toss the panko breadcrumbs in the melted butter and season with salt.
3. Sprinkle the breadcrumb mixture evenly over the stuffed shells.

Step 6: Bake & Broil

1. Preheat the oven to 325°F (160°C).
2. Bake the shells uncovered for 25 minutes, or until heated through.
3. Switch the oven to broil and cook for 1–2 minutes, watching carefully until the breadcrumbs turn golden brown.
4. Remove from the oven and let rest for 5 minutes before serving.

Step 7: Serve & Enjoy

• Garnish with additional chopped parsley.
• Serve warm with a side salad, roasted vegetables, or garlic bread.