In a large skillet over medium heat, melt 2 tablespoons of butter and sauté 3 minced garlic cloves until fragrant, about 1 minute. Add 1 cup of chopped lobster meat and 1 cup of crab meat, stirring gently for 3-4 minutes just until heated through. Remove the seafood mixture from heat and set aside for later, allowing it to cool slightly.

In a mixing bowl, combine the sautéed seafood, 8 ounces of softened cream cheese, 1 cup of shredded mozzarella, 1 teaspoon of salt, and ½ teaspoon of black pepper. Stir until the mixture is smooth and well blended.

Bring a large pot of salted water to a boil. Add 12 jumbo pasta shells and cook according to package instructions, about 9-11 minutes, until al dente. Drain the shells and rinse gently under cold water to stop the cooking process. Lay them out on a towel to cool.

In the same skillet used for the seafood, melt 3 tablespoons of butter over medium heat. Whisk in 2 tablespoons of flour and cook for about 1 minute until bubbling. Gradually pour in 1 cup of heavy cream and ½ cup of grated Parmesan cheese, whisking constantly until the sauce is creamy and thickens, about 3-4 minutes. Season with salt and pepper to taste.

Preheat your oven to 375°F (190°C). Spread a thin layer of the cream sauce on the bottom of a 9x13-inch baking dish. Carefully fill each pasta shell with the seafood mixture, placing them seam-side up in the dish. Pour the remaining cream sauce evenly over the stuffed shells.

Cover the baking dish with aluminum foil and bake for 20 minutes. Then, remove the foil and continue baking for an additional 10 minutes or until the tops are bubbling and golden brown.

Allow the Creamy Seafood Stuffed Shells to cool for about 5 minutes before serving. Garnish with freshly chopped parsley or additional Parmesan cheese if desired.