Bake, covered, for 45 to 55 minutes, or until the potatoes are almost tender when pierced with a knife and the sauce bubbles around the edges.
Carefully remove the foil, being aware of the hot steam. Return the uncovered dish to the oven and continue baking for another 20 to 25 minutes, or until the top has turned a deeper color, the sauce has thickened slightly, and the potatoes are completely tender throughout.
Remove the dish from the oven and let it rest for 10 to 15 minutes before serving. This short rest allows the sauce to set and adhere to the potatoes, making it easier to scoop out neat portions while retaining the rich, dark sauce around the edges.
Serve the potato gratin straight from the white dish, and spoon generous portions of potatoes and plenty of brown sauce onto each plate while it is still warm.
Variations and Tips
For a slightly different texture, you can use a mix of Russet and Yukon Gold potatoes – the Russet potatoes give that soft, almost mashed edge, while the Yukon potatoes hold their shape a little better. If your sauce is mild and you're not strictly counting ingredients, a pinch of black pepper or dried thyme stirred into the canned sauce before layering can add some depth. For a creamier version, replace one can of brown sauce with one can of condensed mushroom soup, whisked together with the remaining sauce before pouring over the potatoes. If you prefer a smaller batch, halve all quantities and bake in a 8x8 inch pan, checking to make sure it's done a little earlier. Leftovers can be reheated nicely in a covered pan in the oven or in the microwave with a splash of water or extra sauce to thin out the sauce. To make this more of a one-pan meal, serve it topped with sliced leftover roast or rotisserie chicken placed over the potatoes for the last 10 minutes of baking so the meat is gently heated in the sauce without drying out.
3-Ingredient Oven-Baked Potato Gratin with Brown Gravy
