Gratin Dauphinois is a basic thing. So basic, in fact, that I can't imagine any reason why people would eat the boxed shit. The garbage dehydrated crap isn't even cheaper. Okay, I'll admit that it is marginally easier to open a box and a couple bags, but you end up having to boil water and milk to pour over the dehydrated potatoes anyway, when you could just slice a couple of real potatoes on your mandoline (or in the processor), dump them in a glass bowl and microwave them in the milk. Then all you do is dump the whole lot into a buttered casserole with a slice garlic clove, top it with cheese, and whack it into the oven for an hour. Easy peasy.
I used 50-50 milk and half & half (so I guess it was 75% milk, and 25% cream), a few pinches of salt and some pepper, and a few scratches of nutmeg. I topped it with the last of the Madrigal cheese and tented some foil over the whole pan to keep the cheese from browning too early.
Serve with a medium-rare ribeye (grilled with only crunchy salt and cracked pepper) and a bitchy red (I like 2006 Three Winds Syrah these days - a little brash and ign'unt, but she calms down if you give her some space. Plus, the label looks like a Kurosawa movie poster).