Gratin Dauphinois Puns

I'm German and living in Spain. I would like to know if "Kartoffelgratin" is something that is known / eaten here.

Edit: I am asking this myself because Spain knows how to make good patatas, so it would be logical to have it here, too, right? On the other hand I have never seen it in a restaurant or something

I've been making a gratin dauphinois for a long time in which I just pour the cold milk/cream mixture over the layered potatoes and bake at low temp. It comes out great. But I've noticed that most scalloped potato/gratin dauphinois recipes call for bringing the dairy to a boil and then pouring it over the potatoes. Jeffrey Steingarten even calls for bringing it to a boil, taking it off the heat, slicing and layering the potatoes, returning the milk to a boil and then pouring it over the potatoes. What function does pre-heating the dairy serve? And can anyone think of why one would bring it to the boil twice?

I'm wondering if I can use pre-cut, slightly parboiled potatoes to cut down on the cooking time.

I've come across multiple recipes that call for parboiling the potatoes in the cream/milk/sauce mixture before pouring them into a dish, but those rely on the parboiling process in the sauce for the potatoes to release their starches to thicken the sauce. I'm guessing pre-parboiled might not have the same effect.

Basically, can I make the sauce, dump the parboiled potatoes in, and just go to the oven? Also if I made it and kept it overnight, would it turn into inedible mush?