Few dishes turn an ordinary dinner into something worth remembering quite like a bubbling tray of au gratin potatoes. Thin layers of tender potato are bathed in a velvety, cheese-laced sauce and baked until golden — rich, comforting, and the kind of side dish people ask for the recipe of.

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Why We Love This Creamy au Gratin Potatoes Recipe

Built on a classic technique — a simple roux-based sauce guarantees a smooth, lump-free result every time

Layered for flavor — sliced onion tucked between the potatoes adds gentle sweetness without overpowering the dish

Sharp white Cheddar delivers bold cheesy flavor while keeping the sauce visually light and appetizing

Low-fuss prep — no pre-cooking the potatoes required; everything bakes together in one dish

Crowd-pleasing and make-ahead friendly — ideal for holidays, potlucks, or a cozy Sunday dinner

Au Gratin Potatoes Ingredients

These are the ingredients you will need to make this top-rated au gratin potatoes recipe:

Russet potatoes – sliced about ¼ inch thick (a mandoline makes quick, even work of this)

Yellow onion – cut into thin rings and layered between the potato slices

Salt and black pepper – the only seasoning this dish needs to let the cheese shine

Unsalted butter and all-purpose flour – whisked together to form the base of the sauce

Whole milk – added gradually to build a silky, pourable cheese sauce

Sharp white Cheddar, freshly shredded – pre-shredded cheese contains anti-caking agents that can make the sauce grainy, so shredding your own is worth the extra step

Step-By-Step Directions

Step 1: Prep your dish. Preheat the oven to 400°F (200°C) and butter a 2-quart baking dish.

Step 2. Start layering. Arrange half of the sliced potatoes across the bottom of the dish. Sprinkle with salt and pepper.

Step 3. Add the onion and finish layering. Scatter onion rings over the first potato layer, then top with the remaining potatoes. Season once more with salt and pepper.

Step 4. Build the roux. In a medium saucepan over medium heat, melt the butter. Whisk in the flour and a pinch of salt, stirring constantly for about a minute until the raw flour smell disappears.

Step 5. Whisk in the milk slowly. Add the milk a little at a time — roughly ¼ cup at a time — whisking thoroughly between additions. Going slowly here is the secret to a smooth, lump-free sauce.

Step 6. Let it thicken. Continue whisking over the heat for 3 to 5 minutes, until the sauce coats the back of a spoon.

Step 7. Melt in the cheese. Add the shredded Cheddar all at once and stir until fully melted, about 30 to 60 seconds.

Step 8. Assemble. Pour the warm cheese sauce evenly over the layered potatoes, then cover the dish tightly with foil.

Step 9. Bake. Place in the oven and bake for about 1½ hours, until the potatoes are fork-tender and the sauce is bubbling at the edges.

Tips For The Best Results

Slice potatoes as evenly as possible — uneven thickness means uneven cooking

Don’t rush the milk addition; pouring it in too fast is the #1 cause of a grainy sauce

Shred your own cheese for the smoothest melt

If the top isn’t golden enough after baking, uncover for the last 10–15 minutes

Let the dish rest for 10 minutes before serving so the sauce can set slightly

Storge

Cool completely, then store in an airtight container in the refrigerator for up to 4 days. Reheat individual portions in the microwave, or warm the whole dish covered in a 350°F oven until heated through. For longer storage, this dish can be frozen for up to 2 months — thaw overnight in the fridge before reheating.

Print Recipe

Creamy au Gratin Potatoes Recipe

Prep Time30

Cook Time1 30

Total Time2

Servings: 8

Ingredients

2 lbs Russet potatoes sliced ¼ inch thick
1 yellow onion sliced into thin rings
1 tsp salt divided, plus more to taste
½ tsp black pepper divided, plus more to taste
4 tbsp unsalted butter
¼ cup all-purpose flour
2 cups whole milk
2 cups sharp white Cheddar cheese freshly shredded

Instructions

Preheat the oven to 400°F (200°C) and butter a 2-quart baking dish.
2. Arrange half of the sliced potatoes across the bottom of the dish. Sprinkle with salt and pepper.
3. Scatter onion rings over the first potato layer, then top with the remaining potatoes. Season once more with salt and pepper.
4. In a medium saucepan over medium heat, melt the butter. Whisk in the flour and a pinch of salt, stirring constantly for about 1 minute until the raw flour smell disappears.
5. Add the milk a little at a time — about ¼ cup at a time — whisking thoroughly between additions to keep the sauce smooth and lump-free.
6. Continue whisking over the heat for 3 to 5 minutes, until the sauce thickens enough to coat the back of a spoon.
7. Add the shredded Cheddar all at once and stir until fully melted, about 30 to 60 seconds.
8. Pour the warm cheese sauce evenly over the layered potatoes, then cover the dish tightly with foil.
9. Bake for about 1½ hours, until the potatoes are fork-tender and the sauce is bubbling at the edges. (Tip: uncover for the last 10–15 minutes if you'd like a more golden top.)

Notes

Store leftovers in an airtight container in the refrigerator for up to 4 days, or freeze for up to 2 months. Reheat covered in a 350°F oven, or in the microwave for individual portions. Let the dish rest 10 minutes after baking so the sauce can set before serving.

Nutrition Facts

Calories: 499
Total Carbohydrates: 49g
- Dietary Fiber: 4g
- Total Sugars: 9g
Protein: 20g
Total Fat: 25g
- Saturated Fat: 16g
Cholesterol: 77mg
Sodium: 683mg
Vitamin C: 19mg
Calcium: 484mg
Iron: 3mg
Potassium: 1184mg

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