Description
This classic Au Gratin Potatoes recipe features thinly sliced russet potatoes layered with a rich, creamy sauce made from caramelized onions, garlic, thyme, Gruyère, and Parmesan cheese. Baked to perfection with a golden, cheesy crust, this comforting dish is perfect for gatherings and pairs beautifully with a variety of mains.
Ingredients
Scale
Vegetables
- 1 small yellow onion (finely diced)
- 4 cloves fresh garlic (minced)
- 2 ½ lbs. russet potatoes (sliced 1/8-inch thick)
- Chives (to garnish)
Dairy
- 3 tablespoons salted butter
- 2 cups heavy cream
- ½ cup milk
- 2 cups shredded Gruyère cheese
- ½ cup grated Parmesan cheese
Herbs & Spices
- 2 teaspoons fresh thyme leaves
- ¼ teaspoon salt
- ¼ teaspoon pepper
Instructions
- Preheat the oven: Set your oven to 350°F (175°C) to allow it to reach the right temperature by the time the potatoes and sauce are ready for baking.
- Prepare cream mixture: Combine heavy cream and milk in a medium measuring cup with a spout. Microwave for 1 minute to warm the mixture, then set aside for later use.
- Caramelize onions: In a soup pot over medium heat, melt butter and add diced onions. Soften them for 10 minutes while stirring frequently, then reduce heat to medium-low and cook another 10-15 minutes until the onions start to brown and caramelize slightly.
- Add garlic and thyme: Stir in minced garlic and fresh thyme leaves, cooking for 2 additional minutes to release their fragrance.
- Combine cream and cheese sauce: Turn off the heat briefly to let the pot cool for 1 minute. Gradually stir in the warmed heavy cream and milk mixture. Increase heat to medium-high and bring to a boil. Remove from heat, then slowly add shredded Gruyère and grated Parmesan, allowing cheese to melt with each addition. Season with salt and pepper.
- Slice potatoes: Using a mandoline slicer or a knife, cut potatoes into 1/8-inch thick slices to ensure even cooking throughout the dish.
- Layer potatoes and sauce: Lightly grease a 2.5-quart or 9 x 13-inch baking dish. Arrange one-third of the potato slices on the bottom, lightly sprinkle with salt, then pour one-third of the cheese sauce over the layer. Repeat two more times to create three layers of potatoes and sauce.
- Bake covered: Cover the dish with foil or a lid and bake in the preheated oven for 1 hour, allowing the potatoes to cook fully and the sauce to meld.
- Finish baking uncovered: Remove cover and bake for an additional 30 minutes to develop a golden top. For extra color and crispness, optionally broil at 425°F for 1-2 minutes, watching carefully to prevent burning.
- Rest and garnish: Take the dish out of the oven and let it rest for 5-10 minutes so the sauce thickens and sets. Garnish with freshly chopped chives before serving.
Notes
- Use a mandoline slicer for uniformly thin potato slices, which ensures even cooking.
- Caramelizing the onions slowly adds a depth of flavor to the cheese sauce.
- For a crunchier top, broil carefully for 1-2 minutes at the end of baking.
- Letting the dish rest after baking helps the sauce thicken and improves slicing.
- This dish pairs wonderfully with roasted meats, salads, or as a hearty vegetarian main.
