Cheesy Au Gratin Potatoes
Thin Yukon Gold potato slices sit in overlapping, slightly upright rows, with creamy Cheddar sauce between the layers and browned cheese on top. Covering the casserole first helps the potatoes soften; uncovering it after adding the finishing cheese gives the surface its golden spots. Keep the slices a uniform thickness and test the center with a knife—a browned top does not always mean the potatoes underneath are tender.
Servings: 8 side-dish servings. Prep: 25 to 30 minutes. Bake: About 75 to 90 minutes, plus a 15-minute rest.
Ingredients for Cheesy Au Gratin Potatoes
- 3 pounds Yukon Gold potatoes, scrubbed (about 1,350g)
- 3 tablespoons unsalted butter (about 45g), plus a little more for the dish
- 2 cloves garlic, minced
- 3 tablespoons all-purpose flour (about 25g)
- 2 cups whole milk (480g)
- 1/2 cup heavy cream (120g)
- 2 1/2 cups freshly shredded sharp Cheddar (about 280g), divided
- 1 teaspoon kosher salt, or to taste
- 1/2 teaspoon freshly ground black pepper
- 2 tablespoons chopped fresh flat-leaf parsley
How to Make Cheesy Au Gratin Potatoes
- Prepare the oven and dish: Preheat the oven to 375°F (190°C). Lightly butter a 9-by-13-inch baking dish, approximately 3 quarts. Set aside 1/2 cup of the Cheddar for the top.
- Slice and arrange the potatoes: Cut the potatoes into uniform slices about 1/8 inch thick. Use a mandoline with its hand guard or a sharp knife. Arrange the slices in compact, overlapping rows tilted slightly upright, leaving narrow gaps for the sauce. Do not compress them into tight vertical bundles.
- Make the roux: Melt the 3 tablespoons butter in a medium saucepan over medium-low heat. Add the garlic and cook briefly, until fragrant but not browned. Whisk in the flour and cook for about 1 minute, stirring, until it forms a smooth paste.
- Finish the sauce: Gradually whisk in the milk and cream. Increase the heat to medium if needed and bring to a gentle simmer. Whisk for about 7 to 10 minutes, until the sauce lightly coats a spoon. Remove from the heat and stir in 2 cups Cheddar, the salt, and pepper until smooth and pourable. Taste and adjust the salt; Cheddar varies in saltiness.
- Sauce the potatoes: Pour the sauce slowly between the rows and across their tops. It should reach into the gaps, though some potato ridges will remain visible. Cover the dish tightly with foil.
- Bake covered: Bake for 45 minutes. Carefully lift the foil away from you to avoid the steam.
- Brown and check: Scatter the reserved 1/2 cup Cheddar over the potatoes. Bake uncovered for about 30 to 45 minutes more, starting to check the center after roughly 25 minutes uncovered. A thin knife should slide easily through slices near the center, not just around the edges. The sauce should bubble, and the cheese should be golden with scattered deeper brown spots. If the top browns before the center is tender, tent loosely with foil and continue baking.
- Rest and serve: Let the gratin rest uncovered for 15 minutes so the sauce settles around the slices. Scatter the parsley over the top, then scoop portions from the dish.
How to Arrange and Sauce the Potato Rows
Lean the slices against one another rather than standing them straight up. The slight tilt keeps their edges visible while leaving paths for sauce to flow between them. Pour sauce over exposed tops as well as into the gaps so the upper slices do not dry out. A substantially smaller or deeper dish can crowd the rows and lengthen the bake.
How to Tell When the Gratin Is Done
Test several spots near the center with a thin knife. If it meets resistance, keep baking even if the cheese is browned; tent the dish loosely with foil if the top is getting too dark. Thicker slices, a deeper dish, or a casserole baked straight from the refrigerator may need more time. After the 15-minute rest, the sauce should cling to a lifted serving rather than run freely.
Potato and Cheese Choices
Scrubbed Yukon Golds can be left unpeeled or peeled for a smoother appearance. Russets also work, though their slices may soften more and hold less definition. Freshly shredded Cheddar melts smoothly into the sauce.
The flour thickens the listed milk-and-cream sauce; omitting it without changing the liquid will produce a different result. For a nuttier variation, replace up to 1 cup of the Cheddar in the sauce with shredded Gruyère, keeping Cheddar for the topping.
Serving and Leftovers
Serve with ham, roast chicken, turkey, or beef, alongside a green salad or roasted vegetables. For another creamy potato side, try creamy garlic mashed potatoes.
The casserole can be assembled ahead and refrigerated. If baking it cold, allow extra time and use center tenderness as the final check. Refrigerate leftovers covered or in an airtight container for up to 3 to 4 days. Reheat covered in a 350°F (175°C) oven until hot throughout, or microwave individual portions until heated through. Freezing is not recommended for best texture: the potatoes may become mealy and the dairy sauce may separate.
Nutrition
Approximate per serving (1/8 of the casserole): 405 calories, 15g protein, 23g fat, and 36g carbohydrates. Approximate per 100g of finished gratin: 155 calories, 6g protein, 9g fat, and 14g carbohydrates. Values are estimates; serving size, cheese brand, and moisture lost during baking will affect them.
Equipment
- 9-by-13-inch baking dish
- Mandoline or sharp knife
- Medium saucepan
- Whisk
- Aluminum foil
Ingredients
For the potatoes and sauce
- 3 pounds Yukon Gold potatoes, scrubbed (about 1,350 g)
- 3 tablespoons unsalted butter (about 45 g), plus more for the dish
- 2 cloves garlic, minced
- 3 tablespoons all-purpose flour (about 25 g)
- 2 cups whole milk (480 g)
- 1/2 cup heavy cream (120 g)
- 2 1/2 cups freshly shredded sharp Cheddar (about 280 g), divided
- 1 teaspoon kosher salt, or to taste
- 1/2 teaspoon freshly ground black pepper
- 2 tablespoons chopped fresh flat-leaf parsley
Instructions
- Preheat the oven to 375°F (190°C). Lightly butter a 9-by-13-inch baking dish, about 3 quarts, and set aside 1/2 cup of the Cheddar for the topping.
- Slice the potatoes uniformly, about 1/8 inch thick. Arrange them in compact, overlapping rows, tilted slightly upright with narrow gaps between the slices.
- Melt the 3 tablespoons butter in a medium saucepan over medium-low heat. Add the garlic and cook briefly until fragrant but not browned.
- Whisk in the flour and cook for about 1 minute, stirring, until a smooth paste forms.
- Gradually whisk in the milk and cream. Bring to a gentle simmer and whisk for 7 to 10 minutes, until the sauce lightly coats a spoon.
- Remove the sauce from the heat. Stir in 2 cups of the Cheddar, the salt, and pepper until smooth and pourable. Taste and adjust the salt as needed.
- Pour the sauce between the potato rows and over their tops. Cover the dish tightly with foil.
- Bake covered for 45 minutes. Carefully lift the foil away from you to avoid the steam.
- Sprinkle the reserved 1/2 cup Cheddar over the potatoes. Bake uncovered for about 30 to 45 minutes, checking the center after about 25 minutes.
- Check the center with a thin knife; it should slide easily through the potato slices. If the top browns before the center is tender, tent loosely with foil and continue baking.
- Rest uncovered for 15 minutes. Scatter the parsley over the top and serve.
Tips
- Keep potato slices a uniform 1/8 inch thick so they cook evenly.
- Use a mandoline with its hand guard or slice carefully with a sharp knife.
- Tilt the potato slices slightly and leave gaps so the sauce can flow between them.
- Check tenderness in several spots near the center; a browned top does not guarantee the potatoes are done.
- Use a 9-by-13-inch dish to avoid crowding the rows and extending the baking time.
Variations
- Cheddar and Gruyère Potatoes: Replace up to 1 cup of the Cheddar in the sauce with shredded Gruyère, keeping Cheddar for the topping.