Melt 2 tablespoons of butter in a skillet over medium heat. Sauté 2 minced garlic cloves until fragrant, about 2 minutes. Add chopped lobster and crab meat, cooking until heated through, around 3–5 minutes. Set aside to cool slightly.

In a large mixing bowl, combine the cooked seafood mixture with 8 ounces of cream cheese and 1 cup of shredded mozzarella cheese. Add salt and pepper to taste; mix until smooth.

Bring a large pot of salted water to a boil and cook 12 jumbo pasta shells until al dente, about 8–10 minutes. Drain and rinse gently with cold water.

In the same skillet, melt 3 tablespoons of butter over medium heat. Whisk in 3 tablespoons of flour for about 2 minutes. Gradually stir in 1 cup of heavy cream and ½ cup of grated Parmesan cheese until thickened.

Preheat oven to 375°F (190°C). Spread a layer of sauce on the bottom of a baking dish. Fill each shell with seafood mixture and place seam-side up. Pour remaining sauce over 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 a few minutes before serving. Optionally garnish with fresh parsley or extra Parmesan.