Modern Mac & Cheese

Not sure how modern this recipe is but the Serious Eats folks called it such and who am I to say no?  I can’t quite get over the melting of the cheese into simmering water instead of a white sauce but it works.I bought this at Amazon.  I’m sure it is going to last a long time unless we go cheese sauce crazy.  I made a half recipe using a pound of shredded cheddar and I have to say the sauce it made is very good.  I used most of it on the mac but had enough left to coat the veggies, too.
I will note that the sauce retains its creaminess longer as it cools instead of setting up. Alas, clean-up is not any faster.