Make the Cheese Sauce:

Melt the butter in a saucepan and stir in the flour. Cook until lightly browned and smooth. Add the milk in a steady stream, whisking to prevent any lumps, and cook until sauce comes to a slight boil and thickens. Stir in the heavy cream. Remove from the heat, stir in the cheese, and season with salt and pepper to taste. Cover to keep warm.

Preheat the oven to 400 degrees F.

To assemble the macaroni and cheese, melt 2 tablespoons of the butter in a sauté pan and add the lobster, macaroni, and 2 ½ cups of the Cheese Sauce. Bring the sauce to a simmer, then fold in the grated cheddar and mix until smooth. Place in a small baking dish.

Melt the remaining 2 tablespoons butter and pour over the crumbs in a small bowl. Stir to blend, then stir in the Parmesan. Sprinkle the crumb mixture evenly over the top of the Mac n Cheese and bake until sauce is bubbly and the crumbs are golden and crispy on top.