For the Mac & Cheese:
Cook the Pasta: Bring a large pot of salted water to a boil. Add the pasta and cook according to the package instructions until al dente. Drain and set aside.
Make the Cheese Sauce: In a medium saucepan, melt the butter over medium heat. Stir in the flour and cook for about 1 minute, until lightly golden. Gradually whisk in the milk and heavy cream, and cook until the mixture thickens, about 5-7 minutes.
Season the Sauce: Stir in the garlic powder, onion powder, Old Bay seasoning, salt, and pepper. Add the shredded cheddar, mozzarella, and Gruyere cheeses, stirring until melted and smooth.
Combine with Pasta: In a large mixing bowl, combine the cooked pasta with the cheese sauce, ensuring the pasta is well-coated.
For the Seafood:
Prepare the Seafood: In a large skillet, melt the butter over medium heat. Add the shrimp, crab meat, and lobster meat (if using). Season with garlic powder and lemon juice. Cook for 3-4 minutes until the seafood is heated through.
Mix with Pasta: Gently fold the cooked seafood into the pasta and cheese mixture.
For the Topping:
Prepare the Topping: In a small bowl, combine the breadcrumbs, grated Parmesan cheese, melted butter, and chopped parsley (if using).
Assemble the Dish: Preheat your oven to 350°F (175°C). Transfer the seafood mac and cheese mixture to a baking dish. Sprinkle the breadcrumb mixture evenly over the top.
Bake: Bake for 20-25 minutes, or until the top is golden brown and the cheese is bubbly.
Serve:
Plate the Dish: Allow the dish to cool for a few minutes before serving.
Garnish: Optionally, garnish with additional parsley or a sprinkle of paprika for color.