Melt butter in a skillet over medium heat and sauté minced garlic until fragrant, about 1 minute. Add lobster and crab meat, cooking for 2-3 minutes until just opaque.

In a mixing bowl, combine the cooled seafood, cream cheese, mozzarella cheese, and season with salt and pepper. Stir until all ingredients are well incorporated.

Bring a large pot of salted water to a boil and cook the jumbo pasta shells according to package instructions until al dente, usually about 9-11 minutes. Drain and rinse under cold water.

In the same skillet, melt more butter over medium heat. Whisk in flour and cook for about 1-2 minutes until golden, then gradually pour in heavy cream.

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

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

Allow to cool for 5 minutes before serving. Garnish with extra parmesan or fresh herbs.