Preheat oven to 375°F (190°C).

Cook elbow macaroni in salted water according to package instructions. Drain and set aside.

In a skillet, cook seafood (shrimp, crab, or lobster) until just cooked through, about 2-3 minutes for shrimp, or 4-5 minutes for firmer fish. Set aside.

In a large saucepan, melt 4 tbsp butter over medium heat. Add minced garlic and diced onion, cooking until translucent, about 2-3 minutes.

Whisk in 3 tbsp flour and cook for 1-2 minutes, making a roux.

Gradually add 1 c milk and 1 c heavy cream while whisking to avoid lumps.

Continue cooking and stirring until the sauce thickens, about 3-5 minutes.

Remove the saucepan from heat and stir in 1 1/2 c cheddar, 1 c Gruyère, and 1/2 c Parmesan until melted and smooth.

Add 1 tsp Old Bay seasoning, 1/2 tsp paprika, and salt and pepper to taste. Stir to combine.

Mix the cooked macaroni into the cheese sauce, ensuring each piece is well coated.

Gently fold in the cooked seafood.

Pour the mixture into a greased 9x13-inch baking dish.

In a small bowl, mix 1/2 c panko breadcrumbs with 1 tbsp melted butter. Sprinkle the breadcrumb mixture over the top of the macaroni and cheese.

Bake for 25-30 minutes, or until the top is golden brown and bubbly.

Let the dish rest for 5 minutes before serving.