I don't have a specific recipe, but when you are cooking with milk, the curdling happens when the milk gets to hot (especially if it boils).
So you may be cooking at too high a temperature.
You can reduce the tendency to curdle by letting the potatoes sit in the milk for a while before it goes in the oven. Some of the starch from the potato dissolves into the milk, and that makes it less likely to curdle (that is why bread and butter pudding does not curdle, becuase of the starch from the bread).
chief feeder and mucker for Music, Spy, Belle and Tiara. Someone else is now feeding and mucking for Chief and Brain (both foxhunting now).
You have to parboil the potatos and then when the dish is assembled you cook at 300 - not above. This will keep from curdling your sauce. Parboiling means less oven time / less chance of curdling.
I make mine roughly as follows....
Start your cream sauce with a roux - equal parts butter and flour. Cook a few minutes before you add your milk / half and half. I use equal.parts of those (so 1 cup of each). A pinch of nutmeg goes a long way in adding flavor to your cream sauce. 1/2 cup of a nice quality parmesan too.
Assemble all in a big casserole and cook for 45 minutes.
Sprinkle breadcrumbs that have been melted in butter over the top during the last 15 minutes of cooking for an extra decandant heart attack inducing finish.
My cousin makes one that curdles, but she layers the potatoes, milk and shredded cheese.
I make a white sauce and melt cheese into it, then layer it and the potatoes in a buttered casserole, finishing with the cheese, seal in foil and bake it off. I take the foil off the last 15 minutes or so. Because DH actually likes the taste of boxed scalloped potatoes, I add a packet of dry French onion soup mix to my white sauce. Makes homemade taste like store bought