Description
This classic Au Gratin Potatoes recipe features thinly sliced Yukon Gold potatoes layered with onions and smothered in a creamy, cheesy sauce made with cheddar, Gruyere, and Parmesan cheeses. Baked to golden, bubbly perfection, this comforting side dish is perfect for holiday dinners or family gatherings.
Ingredients
Scale
Potatoes & Vegetables
- 3 lbs Yukon Gold potatoes, thinly sliced (about 12 potatoes)
- ½ yellow onion, thinly sliced
Sauce
- 4 tbsp unsalted butter (½ stick, plus more for greasing the pan)
- 2 cloves garlic, minced
- ¼ cup all-purpose flour
- 1½ cups whole milk
- 1 tsp kosher salt
- ½ tsp ground black pepper
Cheese
- 1 cup freshly shredded cheddar cheese
- 1½ cups freshly shredded Gruyere cheese (divided)
- ½ cup freshly grated Parmesan cheese
Instructions
- Preheat and Prepare Pan: Preheat your oven to 350°F (175°C). Generously grease a 9×13-inch baking dish with butter to prevent sticking.
- Layer Potatoes and Onions: Arrange thinly sliced Yukon Gold potatoes and yellow onion slices layered evenly in the prepared baking dish. Set aside while preparing the sauce.
- Make the Roux: In a medium saucepan over medium heat, melt 4 tablespoons of unsalted butter. Add the minced garlic and sauté until fragrant, about 1 minute.
- Add Flour: Sprinkle the all-purpose flour over the melted butter and garlic. Whisk continuously until the mixture is smooth and the flour turns a light golden color, approximately 1 minute, to cook out the raw flour taste.
- Incorporate Milk: Slowly pour in the whole milk while whisking vigorously to avoid lumps. Continue whisking until the sauce comes to a gentle simmer and thickens slightly.
- Finish Cheese Sauce: Remove the saucepan from heat. Stir in kosher salt, black pepper, cheddar cheese, and ¾ cup of the Gruyere cheese until fully melted and smooth. Pour this creamy cheese sauce evenly over the layered potatoes and onions in the baking dish.
- Bake Covered: Cover the baking dish tightly with aluminum foil and bake in the preheated oven for 45 to 60 minutes. Check doneness by inserting a knife into the center; potatoes should be tender.
- Bake Uncovered with Cheese Topping: Remove the foil and sprinkle the remaining ¾ cup Gruyere cheese plus the Parmesan cheese evenly over the casserole. Return to the oven and bake uncovered for an additional 15 to 20 minutes until the cheese is melted, bubbly, and lightly browned.
- Optional Broil: For a beautifully browned and crispy cheese crust, switch your oven to broil and cook for 1 to 2 minutes, watching carefully to prevent burning.
- Garnish and Serve: Remove from oven, optionally garnish with fresh herbs such as parsley or thyme, and serve warm as a rich and flavorful side dish.
Notes
- Use Yukon Gold potatoes for their creamy texture and buttery flavor which hold up well during baking.
- Slicing the potatoes thinly ensures even cooking and layering.
- To make slicing easier, use a mandoline slicer carefully.
- You can substitute milk with half-and-half or heavy cream for an even richer sauce.
- Let the dish rest for 10 minutes after baking to thicken the sauce before serving.
- For extra flavor, consider adding a pinch of nutmeg to the cheese sauce.
