Cheesy Potato Gratin Casserole Recipe layers tender Yukon gold potatoes with a garlicky cream bath and a bubbly, browned cap of Gruyere, cheddar, and Parmesan. This side suits holiday feasts, Sunday dinners, and potlucks, and it takes about 1 hour 30 minutes from start to finish. I started perfecting gratin after a frosty Midwest winter, and my family now asks for it on repeat.
Why Cheesy Potato Gratin Casserole Recipe Is Worth It
Cheesy Potato Gratin Casserole Recipe rewards you with silky potatoes, rich sauce, and a golden crust that shatters just a little with each forkful. The dish feels fancy yet uses basic pantry staples, so you win on comfort and convenience. You can assemble it ahead, then bake when guests walk in, which saves your sanity.
The creamy sauce hugs every slice, and the cheese blend brings nutty, sharp, and salty notes. Yukon golds hold their shape and bake tender, so each layer stays distinct. You get pure comfort food without fuss.
Ingredients You Need
Serves 8 to 10
- Yukon gold potatoes, 3 pounds, scrubbed and sliced 1/8 inch thick
- Sub: russet potatoes for a softer, fluffier bite. Slice carefully and bake fully until tender.
- Unsalted butter, 3 tablespoons
- Yellow onion, 1 small, finely minced
- Shortcut: 1 teaspoon onion powder
- Garlic, 3 cloves, minced
- Shortcut: 1 teaspoon garlic powder
- Fresh thyme leaves, 2 teaspoons, chopped
- Sub: 1 teaspoon dried thyme
- Heavy cream, 2 cups
- Whole milk, 1 cup
- Sub: use half-and-half, 3 cups total, for a single dairy option
- All-purpose flour, 1 tablespoon
- Gluten-free sub: 2 teaspoons cornstarch whisked into the cold milk
- Dijon mustard, 1 teaspoon
- Nutmeg, 1/4 teaspoon
- Kosher salt, 2 teaspoons, plus more to taste
- Black pepper, 1 teaspoon
- Gruyere cheese, 1.5 cups shredded, about 6 ounces
- Note: buy blocks and shred for better melt. Bagged shreds work when time runs tight.
- Sharp cheddar, 1.5 cups shredded, about 6 ounces
- Parmesan, 1/2 cup finely grated
- Butter or olive oil spray for the dish
Equipment:
- 9×13 inch baking dish
- Mandoline or sharp chef’s knife
- Large saucepan or skillet
- Whisk and wooden spoon
- Cutting board and box grater
- Aluminum foil
Quick Tips & substitutions
- Slice potatoes thin and even, about 1/8 inch, so the casserole cooks uniformly.
- Dry the potato slices after rinsing. Extra moisture can thin the sauce.
- Use Gruyere for nutty flavor, cheddar for sharp bite, and Parmesan for a savory top. Swap in fontina or Monterey Jack if needed.
- Go gluten-free with cornstarch. Whisk it into cold milk before you add it to the pan.
- Warm the dairy on the stove so it does not break in the oven.
- Season every layer lightly. Potatoes need a bit more salt than you think.
- Assemble a day ahead, cover, and chill. Add 10 to 15 minutes to the bake time if you start from cold.
How to Make Cheesy Potato Gratin Casserole
- Prep: 20 minutes
- Cook: 70 minutes
- Total: 1 hour 30 minutes
- Heat the oven to 375°F. Grease a 9×13 inch baking dish.
- Slice the potatoes 1/8 inch thick. Rinse the slices in cold water, then dry them well with towels.
- Make the sauce: melt butter in a large saucepan over medium heat. Add onion and cook until soft, 3 to 4 minutes. Stir in garlic and thyme, 30 seconds.
- For flour option, sprinkle in the flour and cook 1 minute, stirring. Slowly whisk in heavy cream and milk. For cornstarch option, skip the flour, whisk cornstarch into the cold milk, then pour it and the cream into the pan.
- Whisk in Dijon, nutmeg, salt, and black pepper. Bring the mixture to a gentle simmer and cook until it lightly thickens, 3 to 4 minutes. Taste and adjust seasoning.
- Layer half the potatoes in the baking dish, overlapping slightly. Pour over half the sauce. Top with half the Gruyere and half the cheddar.
- Repeat with remaining potatoes, sauce, and cheeses. Sprinkle Parmesan over the top.
- Cover the dish with foil, tented so it does not touch the cheese. Bake for 40 minutes.
- Uncover and bake until the top turns deep golden and a knife slides through the center with no resistance, 25 to 35 minutes.
- Let the gratin rest for 15 minutes so the sauce sets. Sprinkle a little fresh thyme and serve hot.
Variations
- Bacon and leek: sauté 6 slices chopped bacon, then cook sliced leeks in the drippings. Layer both with the potatoes.
- Jalapeño and pepper jack: swap cheddar for pepper jack and tuck in thin jalapeño slices for gentle heat.
- Caramelized onion and goat cheese: fold caramelized onions into the layers and dot soft goat cheese between them.
- Ham and Swiss: add diced ham and use Swiss in place of Gruyere for a brunch spin.
- Truffle twist: drizzle 1 teaspoon truffle oil over the top before serving for a special-occasion finish.
Ways to Serve Cheesy Potato Gratin Casserole
- Pair with roast chicken, steak, or baked salmon.
- Add a crisp green salad or garlicky green beans for balance.
- Plate it with glazed carrots or roasted Brussels sprouts.
- Serve small squares with fried eggs for a cozy brunch.
- Bring it to holiday dinners next to turkey, ham, or prime rib.
Storage
Let leftovers cool, then cover and refrigerate for up to 4 days. Reheat covered at 350°F until hot, 20 to 25 minutes, then uncover for a few minutes to re-crisp the top. Freeze tightly wrapped portions for up to 2 months, thaw in the fridge, and reheat in the oven. The sauce stays creamiest when you reheat gently and avoid boiling.
Cheesy Potato Gratin Casserole
Cheesy Potato Gratin Casserole is a creamy, comforting dish made with thinly sliced potatoes, layered with cheese, and baked to golden perfection. Perfect as a side for dinner or a hearty lunch.
Ingredients
Instructions
- Preheat oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish with butter.
- In a saucepan, melt butter over medium heat. Add minced garlic and sauté until fragrant.
- Pour in heavy cream and milk. Stir in salt, pepper, and nutmeg. Heat until warm but do not boil.
- Arrange half of the potato slices in the prepared baking dish. Sprinkle half of the cheddar cheese over the potatoes.
- Pour half of the cream mixture over the potatoes and cheese.
- Repeat with the remaining potatoes, cheese, and cream mixture. Sprinkle grated Parmesan on top.
- Cover with foil and bake for 45 minutes. Remove foil and bake for another 15 minutes, or until golden and bubbly.
- Let stand 10 minutes before serving. Garnish with fresh chives if desired.
Notes
Use a mandoline slicer for evenly thin potatoes. You can substitute Gruyere or mozzarella for a different cheese flavor. Let the casserole rest before serving for easier slicing.