Preheat the oven to fan-assisted 160C / 180C / 350F / gas 4.
Cook the macaroni according to the packet instructions till al dente. About 3 mins before the macaroni is done add the asparagus. When done drain, transfer into the baking dish.
Melt the butter in a pot over medium heat before adding in the flour and mixing to form a roux paste. Cook for a couple of mins.
Then slowly whisk in the warm milk a little bit at a time till the milk is all in and you end up with a smooth creamy sauce.
Simmer this sauce for about 8 mins till it thickens before stirring in the nutmeg, cheddar and mozzarella cheese until the cheese is all melted.
Pour the cheese sauce over the asparagus and pasta mix till everything is well coated, top with breadcrumbs, cover with some foil and bake for 30 mins. Take the foil of during the last 10 mins of baking so that the breadcrumbs get even more golden.
Serve with a green salad.