How to Make It
Preheat the oven to 375°. Lightly grease a 3-quart shallow baking dish. In a large bowl, toss the sliced potatoes with the onions and garlic and season with salt and pepper. Heat 2 tablespoons of the fat in each of 2 large skillets. Divide the potatoes between the skillets and cook over moderate heat, turning the potatoes with a spatula, until browned in spots, about 10 minutes. Scrape the potatoes from 1 skillet into the other, add the wine and pan juices to the potatoes and bring to a boil.
Transfer the potatoes and liquid to the prepared baking dish and smooth the surface. Top with the thyme and bay leaf and bake for 30 minutes. Moisten the potatoes with the water and bake for about 25 minutes longer, or until the potatoes are tender and lightly browned. Serve the potato gratin hot.