Description
This PERFECT Au Gratin Potatoes recipe features tender, thinly sliced moderate starch potatoes smothered in a creamy cheese sauce made with Cheddar and Parmesan cheeses. With a rich béchamel base enhanced by onions, garlic, and a blend of milk and cream, the gratin is baked to golden perfection, delivering a comforting and cheesy side dish ideal for gatherings or cozy dinners.
Ingredients
Potatoes
- 2 pounds moderate starch potatoes (such as Russet)
Sauce
- 3 tablespoons butter
- 3 tablespoons all-purpose flour
- 1/2 cup finely chopped yellow onion
- 2 cloves garlic, minced
- 2 cups whole milk
- 1/2 cup heavy cream
- 1 1/2 teaspoons salt
- 1/4 teaspoon freshly ground black or white pepper (optional)
Cheese
- 1 1/2 cups shredded Cheddar cheese
- 1/3 cup grated Parmesan cheese, divided in half
Garnish
- Chopped parsley for garnish
Instructions
- Preheat and Prepare Onion Mixture: Preheat your oven to 350°F (175°C). In a large saucepan, melt the butter over medium-high heat. Add the finely chopped yellow onion and cook for 5-6 minutes until soft and translucent. Stir in the minced garlic and cook for an additional minute, allowing the flavors to develop.
- Create the Sauce Base: Sprinkle the all-purpose flour over the onion and garlic mixture, stirring well to combine. Cook this roux for one to two minutes to remove any raw flour taste. Gradually add the whole milk and heavy cream while stirring constantly to maintain a smooth consistency. Bring the mixture slowly to a boil, then reduce heat and let it simmer until it thickens slightly.
- Add Cheese and Season: Remove the sauce from heat and stir in the shredded Cheddar cheese, half of the grated Parmesan cheese, salt, and optional freshly ground pepper. Stir until all the cheese has melted and the sauce is smooth and rich.
- Combine Potatoes and Sauce: Add the sliced moderate starch potatoes to the sauce in the saucepan, making sure they are fully coated and evenly mixed to distribute the creamy cheese sauce.
- Transfer and Bake: Pour the potato and cheese mixture into a 2-quart casserole dish. Sprinkle the remaining Parmesan cheese evenly on top. Cover the dish tightly with aluminum foil and place it in the preheated oven. Bake for 1 hour or until the potatoes are tender when pierced with a sharp knife—note that baking time might vary depending on the thickness of potato slices.
- Uncover and Brown the Top: Remove the foil and continue baking the gratin uncovered for an additional 20 minutes. This will lightly brown the top and help evaporate excess moisture for a perfect creamy texture without being watery.
- Rest and Serve: Let the dish rest for about 5 minutes before serving to allow the sauce to thicken slightly. If using lower starch potatoes like Yukon Gold, you may need to let it sit a few minutes longer to absorb extra liquid. Garnish with chopped parsley if desired and serve warm.
Notes
- Use moderate starch potatoes like Russet for best texture; Yukon Gold can be used but may result in a slightly soupier dish.
- Slice potatoes uniformly thin to ensure even cooking and tenderness.
- Adjust salt seasoning to taste, especially if using salted cheeses.
- Covering the dish while baking helps cook the potatoes thoroughly, and uncovering toward the end crisps the top.
- Allowing the gratin to rest after baking helps set the sauce and improves serving consistency.
- For a crispy topping, you can add breadcrumbs mixed with butter before the final 20 minutes of baking.