Melt 2 tablespoons of butter in a large skillet over medium heat. Sauté 2 minced garlic cloves until fragrant.

Add 1 cup each of diced lobster and crab meat, cooking just until warmed through—about 2-3 minutes.

Remove from heat and let cool.

In a mixing bowl, combine the sautéed seafood mixture with 8 ounces of cream cheese, 1 cup of shredded mozzarella, and a pinch of salt and pepper. Mix gently until all ingredients are combined.

In a large pot of salted boiling water, cook 20 jumbo pasta shells until al dente—about 9-11 minutes. Drain and set aside.

In the same skillet, melt 4 tablespoons of butter. Sprinkle in 1/4 cup of flour and whisk for 1-2 minutes to create a roux.

Gradually whisk in 2 cups of heavy cream, cooking until thickened—about 3-4 minutes.

Stir in 1/2 cup of grated Parmesan and remaining mozzarella until smooth.

Preheat oven to 375°F (190°C). Spoon a layer of cheese sauce into a baking dish. Stuff each shell with about 2 tablespoons of seafood filling and place in dish.

Pour remaining cheese sauce over the shells, covering well. Cover with foil and bake for 20 minutes, then remove foil and bake for an additional 10 minutes.

Let cool for about 5 minutes before serving. Optionally garnish with fresh herbs or additional Parmesan.