Description
This classic Au Gratin Potatoes recipe features thinly sliced russet potatoes baked in a rich, creamy sauce made with caramelized onions, garlic, thyme, heavy cream, and a blend of Gruyere and Parmesan cheeses. The dish is baked until bubbly and golden, making it a perfect comforting side for any meal.
Ingredients
Potatoes
- 2 ½ lbs. russet potatoes, sliced 1/8-inch thick
Sauce
- 1 small yellow onion, finely diced
- 3 tablespoons salted butter
- 4 cloves fresh garlic, minced
- 2 teaspoons fresh thyme leaves
- 2 cups heavy cream
- ½ cup milk
- 2 cups shredded Gruyere cheese
- ½ cup grated Parmesan cheese
- ¼ teaspoon salt
- ¼ teaspoon black pepper
Garnish
- Chives, chopped
Instructions
- Preheat Oven. Preheat your oven to 350°F (175°C). This step can also be done later after the onions are caramelized.
- Prepare Cream Mixture. Combine the heavy cream and milk in a medium measuring cup. Heat in the microwave for 1 minute to temper, then set aside.
- Caramelize Onions. In a soup pot over medium heat, add diced onions and butter. Cook for 10 minutes, stirring often. Reduce heat to medium-low and continue cooking for another 10-15 minutes, stirring frequently until onions brown and caramelize slightly. Add minced garlic and fresh thyme, cooking for 2 more minutes.
- Combine Cream and Onions. Turn off the heat briefly to cool the pot for 1 minute. Gradually stir in the tempered cream and milk mixture. Increase heat to medium-high and bring the liquid to a boil, then remove from heat.
- Add Cheeses and Seasoning. Slowly stir in shredded Gruyere and grated Parmesan, allowing them to melt gradually. Season the sauce with salt and black pepper, stirring to combine well.
- Slice Potatoes. Slice the russet potatoes very thinly, about 1/8-inch thick, using a mandoline slicer if available for uniform slices.
- Layer Potatoes and Sauce. Lightly grease a 2.5-quart or 9 x 13-inch baking dish. Arrange one-third of the potato slices in the bottom, sprinkling lightly with salt. Pour one-third of the cheese sauce over the potatoes. Repeat two more times to layer potatoes and sauce evenly.
- Bake Covered. Cover the baking dish and bake in the preheated oven for 1 hour.
- Finish Baking Uncovered. Remove the cover and bake for an additional 30 minutes. For a more golden and crispy top, optionally broil at 425°F for 1-2 minutes, watching carefully to avoid burning.
- Rest and Serve. Remove from oven and let rest for 5-10 minutes to allow the sauce to thicken. Garnish with chopped chives before serving.
Notes
- Use a mandoline slicer for uniform potato slices to ensure even cooking.
- Lightly salting each potato layer enhances flavor throughout the dish.
- Broil carefully and watch closely when adding color to the top to prevent burning.
- Russet potatoes are preferred due to their high starch content and creamy texture when cooked.
- Prep Time: 40 minutes
- Cook Time: 1 hour 40 minutes
- Category: Side Dish
- Method: Baking
- Cuisine: French
