This Mac and Cheese is pure decadence. It gets a unique complexity from herbs that are steeped in the milk used to make the bechamel, with a tiny kick of spice. The breadcrumb topping really knocks it out of the park.
This dish is great for freezing. I go through step 4 above and let the assembled casserole cool slightly. Then I press some plastic wrap down over the surface of the mac and cheese, and cover the entire dish with aluminum foil. First, cool completely in the refrigerator, then transfer to the freezer. You can pull the casserole out to thaw up to 2 days in advance, then complete step 5. OR, you can take it directly from the freezer to the oven: remove the plastic wrap, top with breadcrumbs and cheese, and recover with foil. Bake at 400 degrees for 1 hour, then remove the foil and continue baking until the topping is golden.