Au Gratin Potatoes

These decadent Au Gratin Potatoes are the ultimate side dish for any special occasion. They feature thinly sliced potatoes smothered with a rich homemade cream sauce and the robust flavor of Gruyere cheese. They’re heavenly.

Ingredients to Make Au Gratin Potatoes Recipe

Have you ever wondered the difference between scalloped potatoes and au gratin potatoes? Food purists will tell you that scalloped potatoes recipes don’t include cheese and are basically thin potatoes cooked in a cream sauce making them more simple by nature. Au gratin potatoes tend to be a bit more decadent and the recipe is a bit more involved typically layered with lots of cheese. I have used the terms interchangeably from time to time and tend not to get too terribly fussy about the titles of my potato recipes. We’re an equal opportunity potato loving family so regardless of what they’re called to us, it all spells delicious served for family dinners, with turkey at Thanksgiving or Easter and Christmas with ham. Ingredients to make authentic Southern Au Gratin Potatoes: (Scroll down for full printable recipe card.)

• Potatoes – Four pounds russet potatoes.
• Onion – Finely diced sweet onion or yellow onion.
• Butter – Salted butter to make the sauce.
• Flour – All purpose flour to make the roux.
• Seasonings – Salt, black pepper, ground mustard and ground nutmeg.
• Garlic – One large garlic clove, finely minced.
• Herb – Fresh thyme leaves for the cheese sauce and garnishing.
• Milk – Two cups whole milk or half and half make the sauce creamy.
• Shredded Cheese – Two cups shredded Gruyere cheese give the sauce a nutty flavor.
• Grated Cheese – Grated Parmesan cheese for the cheese sauce and to sprinkle on top.

How to Make the Best Au Gratin Potatoes

• Prepare Dish and Heat Oven -Preheat oven to 375°F. Butter a 11×8-inch baking dish.
• Slice Russet Potatoes – Thoroughly clean potatoes and slice thinly using a mandolin slice.
• Make the Sauce –  In a large pot, melt butter over medium heat. Add onion and garlic, cooking until softened.
• Add All Purpose Flour to Make Roux – Season with salt, black pepper, ground mustard and nutmeg.
• Liquid – Gradually whisk in milk and thyme. Simmer on low to thicken.
• Add Cheese – Add Gruyere and Parmesan cheese to sauce, Stir well.
• Assemble Southern Au Gratin Potatoes – Layer potato slices fanned and overlapping in greased baking dish. Pour sauce on top. Sprinkle top with remaining cheese mixture.
• Oven – Cover with aluminum foil and bake per the recipe until the top is golden brown and the potatoes are fork tender.
• Serve – Let potatoes au gratin stand for a few minutes then serve garnished with fresh thyme.

Tips for Making Au Gratin Potatoes

• Kitchen Tools You’ll Need: A 3 quart baking dish either oval or rectangular, a mandolin or food processor, whisk, pot or saucepan, measuring cups and spoons, heavy bottomed saucepan, cheese grater, sharp knife and cutting board.
• Thin Slices Work Best: The potato slices for classic au gratin potatoes need to be super thin. This can be done by hand but for uniform size, a mandolin or a food processor is best.
• Overlap the Layers of Potatoes: When layering the potatoes, you should overlap them as you arrange them in the dish. You could use an oval dish as I did or a 13×9-inch rectangular dish or pan.
• The Garlic is Meant to Be Subtle: The homemade sauce for these potatoes features a hint of garlic. You can adapt the flavor using more garlic cloves, if that’s your preference. In this application, it doesn’t have to be a bold flavor but it’s main role is that of enhancing and not dominating, the flavor of the sauce.
• Keep a Bowl of Cold Water Nearby: If you choose to slice the potatoes by hand, have nearby a large bowl filled with cold water. Place sliced potatoes in the water to keep them from turning brown while you work. Drain well and pat dry before assembling the casserole so the potatoes won’t become watery.
• Make-Ahead Tip: Since the potatoes are raw in this recipe, it’s not ideal to make it in advance and chill until baking. The potatoes will naturally oxidize and turn brown.
• What to Serve with Au Gratin Potato Casserole: These potatoes are special enough for entertaining and holiday meals. They go well with ham, turkey, steak, pork or roasted chicken.

Recipe Variations

• Cheese: I use Gruyere cheese for this recipe. As always, you could adapt using another variety of cheese such as sharp cheddar cheese, gouda cheese or colby jack cheese, according to your taste or what you have on hand. For special occasions, Gruyere is the way to go.
• Milk: Whole milk works very well for the sauce. If you really want to go for the gold, use half and half or heavy cream.
• Butter: You can use unsalted butter for the sauce. Taste and add more salt to your taste to accommodate.

Storage and Leftovers

• Leftovers: Store baked Au Gratin Potatoes in an airtight container chilled in the refrigerator for up to 3 days.
• Reheating: Reheat in single servings in the microwave or in a 350°F oven just until heated through. Lay a piece of foil on top to prevent over browning.
• Freezer Storage: You can freeze baked Southern Au Gratin Potatoes for up to 2 months. Thaw in the fridge and reheat in the oven.

More Easy Potato Recipes to Make

• Cheesy Potato Pancakes can be enjoyed at any meal.
• Nested Potato Skins have been a fan favorite year after year.
• Grilled Garlic Rosemary Smashed Potatoes are the perfect easy side dish for summer grilling.
• Make ahead Cheesy Mashed Potato Casserole.
• Loaded Potato Cakes are a tasty way to stretch mashed potatoes into a round two meal.
• Make these Cheesy Ranch Potatoes in your slow cooker on busy cooking days.
• Sausage Chicken and Potato Kabobs from Miss in the Kitchen.

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Helpful Kitchen Items:

• Casserole Dish
• Cheese Grater
• Saucepan
• Mandolin