Melt 2 tablespoons of butter in a large skillet over medium heat. Sauté minced garlic for about 1 minute until fragrant, then add lobster meat and crab meat. Cook for 2-3 minutes, then set aside to cool slightly.

In a medium mixing bowl, combine sautéed seafood with cream cheese, shredded mozzarella cheese, and a pinch of salt and pepper. Stir until well blended and creamy.

Bring a large pot of salted water to a boil and cook jumbo pasta shells according to package instructions until al dente, about 10-12 minutes. Drain and rinse under cold water.

In the same skillet, melt 4 tablespoons of butter over medium heat. Whisk in flour and cook for about 1 minute. Gradually add heavy cream, stirring, then mix in grated Parmesan and shredded mozzarella until smooth.

Preheat the oven to 375°F (190°C). Spread a thin layer of cheese sauce on the bottom of a baking dish. Fill each jumbo shell with the seafood filling and arrange them in the dish. Pour the remaining cheese sauce over the shells.

Cover with foil and bake for 20 minutes. Remove foil and bake for an additional 10 minutes until bubbly and golden.

Let cool for about 5 minutes, garnish with extra Parmesan or herbs, and serve warm.