Preheat the oven to 375°F. Cook the jumbo pasta shells according to package directions. Drain and let the shells dry on a layer of paper towel.
24 jumbo pasta shells
Heat the oil in a large skillet over medium heat. Add in the onion and a sprinkle of salt. Cook for a few minutes until softened. Add in the garlic, and cook for another minute.
½ tbsp olive oil, ½ onion, ½ tsp salt, 3 cloves garlic
Add in the shrimp and crab meat, and sprinkle with Old Bay seasoning. Cook for a couple minutes until the shrimp is pink.
8 oz. raw peeled and deveined shrimp, 18 oz. lump crab meat, ½ tsp Old Bay seasoning
Transfer the shrimp and crab mixture to a large bowl. Add in the lemon juice, cream cheese, mayonnaise, and 2 tablespoons chopped parsley. Stir to combine.
2 tsp lemon juice, 4 oz. cream cheese, ¼ cup mayonnaise, 2 tbsp chopped parsley
In a saucepan, melt the butter. Once melted, whisk in the flour until smooth. Stir in the salt, pepper, and garlic powder. Slowly pour in the milk and heavy cream while whisking. Let the mixture simmer for a couple minutes until thickened.
3 tbsp butter, 2 tbsp flour, pinch pepper and garlic powder, 1½ cups milk, ½ cup heavy cream
Pour ½ cup of the sauce in the bottom of a greased casserole dish.
Scoop the seafood filling into each shell and place in a greased casserole dish. Pour the remaining sauce over the shells.
In a bowl, combine the breadcrumbs and melted butter. Sprinkle the breadcrumbs and Parmesan cheese over the shells.
½ cup breadcrumbs, 2 tbsp butter, 2 tbsp grated Parmesan cheese
Bake for 25 minutes until the top is golden brown and the sauce is bubbling. Top the shells with chopped parsley and additional grated Parmesan cheese.