Looking for one that's not super rich.
Use stock in place of cream. It's a lovely change-up.
Very sorry, Kristen. I didn't mean to be so cryptic, but I also sort of figured you knew your way around a potato. Okay, so as the collective wisdom suggests, peel them, rinse them, then slice very thinly. A mandoline is perfect here. The thinner the better. Brush the inside of your baking wish with melted butter. Top each layer of potatoes with a layer of Panko. It will help with thickening and also add a lovely layer of flavor and texture. Salt and pepper each layer, then add stock (chicken or vegetable) just until it comes up even with the panko. Repeat until you've used up all the potatoes. If you wait to add stock until the baking dish is full, you risk not adding enough to cook the potatoes because you can't really tell if it's evenly distributed throughout the dish. Hope this helps.
Oh, sorry, forgot the cheese. Gruyère is wonderful here. Scatter some over each layer of Panko and on the top as well. If you're foregoing the cream, you can afford the cheese.
Oh, Kristen. I thought you were a potato-pro! I like to wash the potatoes and slice them very thinly on a mandoline, then fan them out in a gratin dish, and almost cover with cream, gruyere and lots of cracked black pepper. Repeat! Two or three layers is optimal. Then, into the oven at 350 for as long as it takes for the potatoes to cook through and the top to be bubbly and brown!
Having had raw potatoes and thin sauce I finally made the sauce before pouring over the potatoes. Make a roux with butter and flour, add a bay leaf, slowly add chicken broth and still until incorporated and desired thickness. Layer the potatos, and over each layer I add the grated cheese of my choice mixed with thyme. Add sauce, cover with foil bake at 350 til potatoes are done and last 10 minutes or so uncovered so the top browns.
I use layers of Panko to get past the thin sauce issue, plus it adds a nice texture.
I'm not sure if it is the technique or the addition of bacon but I love the texture of Suzanne Goin's Potato Bacon Gratin from Sunday Supper's at Lucques. She has you slice the potatoes super thin (1/16th inch) and the slices all sort of meld together as they cook. Really my favorite gratin I've ever made.
I've always loved Jeffrey Steingarten's technique of making a very thin, very large gratin -- more crispy edge for everyone!