Introduction

There are side dishes… and then there are au gratin potatoes—the kind that steal the spotlight the second they hit the table. These Creamy Cheddar Au Gratin Potatoes are all about thinly sliced potatoes layered with onion, then blanketed in a silky cheddar cheese sauce that bakes into tender, melt-in-your-mouth perfection.

What makes this version so satisfying is the homemade roux-based sauce. It starts with butter and flour (classic), then milk is whisked in until thick and creamy, and cheddar is melted right in. Once poured over the potatoes, the oven does the rest: first covered to cook everything through, then uncovered to get those gorgeous golden spots on top.

This is the side you bring out for Sunday dinner, potlucks, and holidays—because it always disappears fast.

Why You’ll Love This Recipe

• Creamy, cheesy, and deeply comforting

• Homemade sauce (no canned soup) for better flavor

• Perfect for holidays but easy enough for weekends

• Make-ahead friendly and reheats beautifully

• Vegetarian crowd-pleaser

Equipment

• 2½–3 quart shallow baking dish

• Medium saucepan

• Whisk

• Cutting board + sharp knife or mandoline (optional)

• Measuring cups/spoons

• Foil + cooking spray

Ingredients

For the Potatoes

• 4 large baking potatoes (about 2 lb), peeled and sliced ¼-inch thick

• 1 medium onion, sliced into ¼-inch rings

• ¾ tsp salt, divided

• ¼ tsp black pepper, divided

For the Cheese Sauce

• 3 Tbsp butter (cut into pieces)

• 3 Tbsp all-purpose flour

• 2 cups milk (whole milk makes it richest, but any milk works)

• 1½ cups shredded cheddar cheese (about 6 oz)

Optional Add-Ins

• ½ tsp garlic powder (stir into sauce)

• Pinch of cayenne or smoked paprika (for warmth)

• Fresh thyme or parsley (for topping)

• Swap cheddar for a mix of cheddar + Gruyère for extra depth

Step-by-Step Instructions

1) Prep the pan and oven

Preheat oven to 400°F. Spray a 2½–3 quart shallow baking dish with cooking spray. Spray one side of a sheet of foil (this prevents sticking).

2) Layer the potatoes and onion

Layer half the potatoes in the dish. Season lightly with salt and pepper.
Add the sliced onion, then top with the remaining potatoes. Season again.

3) Make the creamy cheddar sauce

In a saucepan over medium heat, melt butter. Whisk in flour and remaining salt until it forms a smooth paste (about 1 minute).
Increase heat to medium-high and slowly whisk in milk. Bring to a gentle boil, whisking constantly.
Reduce heat and simmer 1 minute until thickened. Remove from heat.
Stir in cheddar a little at a time until fully melted and smooth.

4) Bake

Pour sauce evenly over the potatoes. Cover with foil greased side down.
Bake 1 hour, then uncover and bake 20 minutes more, or until potatoes are fork-tender and the top is golden.

5) Rest and serve

Let stand 10 minutes before serving (it thickens as it cools). Sprinkle herbs if you like.

Tips for Best Results

• Slice evenly: ¼-inch slices cook at the same speed—mandoline helps a lot.

• Keep whisking the sauce: This prevents lumps and keeps it silky.

• Shred your own cheese: Pre-shredded can be a little grainy because of anti-caking agents.

• If the top browns too fast: Tent loosely with foil for the last 10 minutes.

• Want extra golden top? Broil for 1–2 minutes at the end (watch closely).

Variations

Slow Cooker Version

Layer potatoes + onion in the slow cooker as directed. Make sauce the same way, pour over, cover, and cook on LOW 5–6 hours until tender.

Extra Creamy

Replace ½ cup milk with ½ cup half-and-half.

Add Protein

Stir in cooked crumbled bacon or diced ham between layers (not vegetarian anymore, but delicious).

More Flavor

Add sautéed mushrooms or caramelized onions instead of raw onion.

Storage & Make-Ahead

• Fridge: Store covered up to 4 days.

• Reheat: Bake at 350°F until hot (add a splash of milk if it looks dry).

• Make ahead: Assemble, cover, and refrigerate up to 24 hours before baking. Add 10–15 minutes to covered bake time.

Serving Suggestions

Perfect with:

• Roast chicken, turkey, or meatloaf

• Grilled steak or salmon

• A crisp green salad to balance the richness

Time Breakdown

• Prep: 25 minutes

• Bake: 1 hour 20 minutes

• Total: 2 hours 5 minutes

• Serves: 6

Nutrition (Provided)

Per ½ cup: 329 cal; 18g fat (11g sat); 12g protein; 31g carbs (2g fiber, 6g sugars); 563mg sodium.

FAQ

Can I use Yukon Gold instead of baking potatoes?

Yes—Yukon Golds get extra creamy and buttery. Baking potatoes (russets) give a softer, fluffier texture.

Why are my potatoes still firm?

Usually the slices were too thick, the dish was too deep, or it needed more time covered. Keep baking covered until fork-tender.

Can I freeze au gratin potatoes?

You can, but the sauce may separate slightly after thawing. It’s best fresh or refrigerated for a few days.

Conclusion

These Creamy Cheddar Au Gratin Potatoes are classic comfort food done right: tender potato layers, sweet onion, and a homemade cheddar sauce that bakes into a golden, bubbly masterpiece. Make it once—and it’ll earn a permanent spot in your side-dish rotation.