Bring a large pot of water to a boil. Cook the macaroni until still very firm, about 4 minutes (it should be too firm to eat right out of the pot). Drain and set aside.
Meanwhile, preheat the oven to 350 degrees F. Generously butter a 9-by-13-inch baking dish. Melt 2 tablespoons butter in a large skillet over medium-high heat. When it just starts to brown, throw in the lobster and cook 1 minute. Transfer to a bowl and set aside.
Add the remaining 4 tablespoons butter to the same skillet. Sprinkle in the flour, whisking to combine. Let the roux cook for a minute or so, whisking constantly. Pour in the milk, whisking constantly, then cook the white sauce until thick and bubbling, 3 to 5 minutes. Next, add the half-and-half, 1 teaspoon salt and plenty of pepper, and stir to combine. Add the parmesan (hold back some for topping!), cheddar, fontina and goat cheese and stir them around to melt. Stir in the lobster and macaroni.
Pour the mac and cheese into the prepared baking dish and top with the reserved parmesan. Bake until bubbling and a slight crust forms on top, 20 to 25 minutes.