I made potatoes au gratin from scratch for the first time today. I made a roux, added milk, melted a slice of American cheese (not ‘cheese food’ or ‘food product’) and a handful of shredded Tillamook medium cheddar into it, then stirred in peeled and sliced Russet potatoes. I baked it in the toaster oven at 350ºF until it was done, then moved it higher in the toaster oven and boosted the temperature to 375ºF.
Mrs. L.A. really liked them.
[quimby]Potatoes au gratin, that’s a quality side.[/q]
With leftover meatloaf from last week. 
Try gratin Savoyard..
Thin-sliced (mandolined) peeled spuds in a buttered casserole rubbed with a split garlic clove, salt and pepper, cover with shredded Gruyere, another layer of potatoes…pour in hot chicken or beef broth (less than you think it needs, maybe 3/4 cup), add more S&P and Gruyere. Bake at 375 for 40 minutes or until cheese and top layer browns and broth is absorbed.
The gratin I usually make is made with Yukon Gold’s peeled and sliced thin, layered in a buttered baking dish with salt/pepper, grated Parmesan and cream warmed/infused with garlic and thyme. Make sure you end up with a layer of Parmesan on the top for a crunchy crust.
The cream combined with the Parmesan and starch from the potatoes forms a thick sauce while baking.
I usually just make a cheezy cream sauce stove-top and stir in the cubes of boiled potatoes. Close enough. I’m not into fussy things.
Made them for the first time in honor of Columbus Day.
(Not really. It was rainy fall day and it seemed like the necessary thing to do.)
I contemplated Julia Child’s recipe which seemed simple. Too simple. So I went with Ina Garten’s instead. Ina’s trick is to saute some fennel and onion. I did one better with fennel and leeks. Of course the milk and cream was simmered with a clove of garlic, fresh sprigs of thyme, fresh ground pepper and a hint of nutmeg. Then meticulous layers of mandolined potatoes, gruyer, sauted fennel/leek, seasoning, milk/cream. Bake at 375F (longer than expected). The result was absolutely spectacular. Not heavy/rich at all as I expected them to be. Perfectly accompanied by champagne. My wife called them “delicate”. Which is high praise as she has a very refined palate.
Definitely doing it again. Perhaps a little more gruyer next time.