Easy Potatoes au Gratin Recipe

Potatoes Au Gratin, a spectacular side dish originating from the Dauphiné region of France, transforms humble potatoes into a truly decadent experience. While the term “au gratin” typically implies a topping of cheese and bread crumbs, this recipe focuses on a luscious, silky béchamel sauce layered between thinly sliced potatoes. This rich, creamy, and cheesy casserole is perfect for elevating a weeknight dinner or serving as the centerpiece side at a potluck or large gathering. The secret to its spectacular texture lies in the starchy potatoes, which help bind the dish together, and the deeply flavorful cheese sauce that bathes the soft potatoes.

Ingredients

For the Potatoes and Seasoning

• 3 lbs Russet potatoes (Yukon Gold may also be used)
• 1 large onion
• ½ teaspoon salt (for seasoning potatoes)
• ¼ teaspoon black pepper (for seasoning potatoes)

For the Béchamel Cheese Sauce

• ¼ cup unsalted butter (approximately 56 g)
• 3 tablespoons flour
• 2 cups whole milk, warmed (to 100°F to 110°F)
• ½ cup shredded Gruyère cheese (similar to Swiss cheese)
• 1 cup shredded flavorful Cheddar cheese (white, yellow, or red)
• ¾ teaspoon salt (for seasoning sauce)
• ½ teaspoon black pepper (for seasoning sauce)

Instructions

1. Preparation and Slicing

1. Preheat your oven to 350°F.
2. Peel the potatoes, rinse them if necessary, and thinly slice them to approximately an 1/8th of an inch thick. Aim for nice, thin slices so they cook evenly.
3. Halve the large onion and cut it into thin slices.
4. Season the sliced potatoes by transferring them to a bowl or sprinkling directly with ½ teaspoon of salt and ¼ teaspoon of black pepper, mixing gently to distribute the seasoning.

2. Assembly

5. Select a 2-3 quart baking dish (an 8-inch x 8-inch dish is suitable).
6. Begin laying out the potato slices in stacks, shingling them across the bottom of the dish.
7. Lay thin slices of onion between every few layers of potatoes; these will melt away during the baking process and add flavor.
8. Continue layering until the casserole dish is full. If you have excess onion, you do not need to use the entire amount—only use enough to introduce flavor.

3. Creating the Cheese Sauce (Béchamel)

9. Grab a medium pot and place it over medium heat.
10. Add ¼ cup of unsalted butter and allow it to melt.
11. As soon as the butter is melted, sprinkle in 3 tablespoons of flour while constantly whisking to prevent lumps.
12. Cook the roux (the mixture of butter and flour), whisking constantly for 2 minutes, until the mixture begins to toast and takes on a slight color.
13. Slowly drizzle in the warmed whole milk (100°F to 110°F) while continuously whisking; the warm milk and constant motion will help maintain a silky base and prevent lumps.
14. Continue cooking and whisking until the mixture begins to bubble and thickens slightly, indicating the flour is active.
15. Remove the pot from the heat. It is important to add the cheese off the heat to prevent it from breaking.
16. Stir in the ½ cup of Gruyère cheese and 1 cup of Cheddar cheese until completely melted and smooth.
17. Add ¾ teaspoon of salt and ½ teaspoon of black pepper to the cheese sauce and stir until combined.

4. Baking

18. Pour the béchamel cheese sauce directly over the assembled potatoes and onions, ensuring full coverage. Smooth the top if needed.
19. Cover the baking dish tightly with foil.
20. Bake in the preheated 350°F oven for 1 hour, covered.
21. After 1 hour, remove the foil and bake for an additional 20 to 30 minutes, or until the top is golden brown.
22. Allow the potatoes au gratin to cool slightly before serving. The resulting dish should feature soft, creamy potatoes bathed in a cheesy sauce.

Optional Tips

• Make Ahead: This dish can be assembled completely the night before and refrigerated, ready to bake the next day.
• Reheating (Pre-Baking): The dish can be baked for 1 hour, allowed to cool completely, refrigerated, and then reheated 40 minutes a day or two later. When reheating, add an extra ¼ cup of cream or milk over the top to ensure it does not dry out.
• For Extra Sharpness: If desired, you may sprinkle an additional ½ cup of Parmesan cheese directly over the top of the casserole before baking.
• Appearance Note: Do not worry about creating a perfect pattern when shingling the potatoes, as the dish will be completely covered in the cheese sauce and will transform into a large mountain during baking.