Prepare macaroni, and while it's cookin', start shredding cheese (if it isn't already shredded).
Preheat oven to 350 - have a 13x9 rectangular baker ready, but be sure to prepare to have something else, in case its too full (I always end up making 1 1/2 pans worth, at least)
Drain the pasta, putting it back into the pot, add butter in first (remember!?!), coating the pasta well.
After whisking the eggs, mix in the milk.
Add the cheeses and seasonings to the pasta, stirring quickly to get it mixed well, then add into the pasta the milk/egg mixture.
Once cheese is melted and covered evenly, add breadcrumbs until covered, and place mixture into baking pan.
Cover and cook for 20 or so minutes.
Take cover off, cook for an additional 5, browning the top.
You can add additional cheese to the top before browning