Ya know, taters Au Gratin are simple to make, but they take time. Especially if you caramelize the onions. This is not a bad thing.
Update: Sheese! You post something about cheesy taters and get yelled at for not posting a recipe? Hehe. Okay, JP, here it is.
Pick an oven safe casserole dish. Pick out enough potatoes as can fill it leaving about half an inch. Peel them. (You can leave the skins on if they are thin skinned like Russets, but we use locally grown taters that tend to be a little green under the peel.) Slice the taters into disks and throw them in the dish.
In a medium sauce pan, melt a quarter stick of butter on a high temperature ... NOT margarine. (Margarine is an invention of the Devil, you know.) Slice one small onion into rings (I tend to chop them, but that's just me. I like using the knife.) Sautee the onions in the hot butter until slightly translucent. Then pour in some kind of sweet white cooking wine just to top the onion. ( I use dryer white wine because it's cheap, but you don't get as thick a caramalization that way. If the wine is too dry, you won't get any caramalization at all.) Turn down the heat to medium low, and cover the simmering onions in the pan, stirring occasionally. (I throw in a teaspoon of crushed garlic at this point, but it is not required. It's all to taste.) You want to wait until the reduce is kinda soupy, and coats the onions in a thick sheen.
Seriously, you can use any kind of hard cheese you want. I tend to use medium cheddar, again because it's cheap. But don't, under any circumstances, use a light, low quality, low-fat or imitation cheese. That's for the same damned reason you don't use margarine. Those things are made with milk fat mixed with ve-hegitable oil. The oil will separate and you will get a mess. Don't do that.
Shred a couple of cups of cheese. I don't have a definitive amount that I use, because it will depend on how many taters you have. A couple of handfuls is probably good. This is the important part, though. Be prepared to keep stirring. Turn the heat to medium/medium high and throw the shredded cheese in with the onions and keep stirring. With the hand that you are not stirring with, pour in about half a cup of any combination of milk and cream. I use about a quarter of a cup of each. Again, I stress that reduced fat products are evil. Ve-hegitable oil is the enemy of good cooking, and animal fat is its geatest good. Keep stirring. Don't stop stirring.
Are you still stirring? Good. The mixture becomes very creamy and tasty in a short period of time. DON'T let it burn or curdle to the pan. I don't put salt in or really any seasonings at all to speak of, but remember, this is to your taste. I prefer to salt after it has baked. Sometimes a tablespoon of rosemary is a nice touch, but don't add it until you have the cheese sauce ready to go.
When you have creamy cheesy goodness, simply pour it over the waiting taters in the casserole dish, and stir or toss the mix. If I have leftover shredded cheese, I put it on the top. Cover and place in a 350 degree oven. Preheat or not, your choice (I do). Again, you got choices. If you bake at 375, it will be done in about an hour and 15 minutes. At 350, about an hour and a half, but it will be more al dente, solid to the bite. If you really want to be fancy, about 20 minutes before it's done cooking, you can add bread crumbs to the top, seasoned bread crumbs even. But why gild the lily? I will state this. If you have used ve-hegitable oil based products, you will have to do the breadcrumbs. No lie. Serve with whatever else you would like, sausages, chicken breasts, steak ... whatever. In a perfect world, this would always be served with the food of angels ...
HAM.
Taters au gratin is really peasant fare. It is simple and delicious. You don't need to caramelize the onions, and you don't need to take a whole lot of time making it. It is simply potatoes and cheese. But to my Celtic-Tuetonic mutt self, it's soul food.