Easy Potatoes Au Gratin with Gruyère

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These potatoes au gratin are made with thinly sliced potatoes layered with nutty Gruyère and Parmesan, then baked in a garlic and thyme-infused cream sauce until tender, bubbling and golden. Rich and comforting without being complicated, they’re an easy make-ahead side dish for Sunday dinner, Thanksgiving, Christmas or any meal that calls for seriously good cheesy potatoes.

Potatoes au gratin with gruyere in a baking dish with fresh thyme.

Serve them alongside my roast leg of lamb or one-pot roast chicken, with maple-glazed carrots for an easy vegetable side.

Table of Contents

Why this recipe works

Two cheeses, two jobs: Gruyère melts beautifully into the layers, while Parmesan adds a sharper, savory finish.
Creamy without a flour-thickened sauce: The natural starch from the potatoes helps thicken the cream as the gratin bakes.
Evenly cooked layers: Thin, uniform potato slices cook at the same rate and absorb the seasoned cream.
Garlic, thyme and nutmeg: These classic flavors add depth to the cream without overpowering the potatoes and cheese.
Golden top, tender center: Baking the gratin covered first allows the potatoes to become tender before uncovering it to brown the cheese.
Perfect for entertaining: This is an impressive but straightforward side dish that’s especially good for holiday dinners and Sunday roasts.

Ingredients Overview

Potatoes: Yukon Gold potatoes are ideal for their naturally buttery flavor and creamy texture. Russet potatoes also work well and release plenty of starch as they bake, helping to thicken the cream.
Gruyère cheese: Melts smoothly between the potato layers and adds its distinctive rich, nutty flavor.
Parmesan: Adds salty, savory depth and helps create the beautifully golden topping.
Heavy cream and whole milk: The combination creates a luxurious sauce without making the gratin excessively heavy.
Garlic: Adds savory depth to the cream and complements the potatoes and cheese.
Fresh thyme: Adds a subtle earthy flavor that works particularly well with Gruyère.
Nutmeg: Just a small amount adds warmth and enhances the creamy sauce without making the gratin taste noticeably of nutmeg.
Butter: Used to generously grease the baking dish, adding flavor and helping prevent the potatoes from sticking.
Salt and black pepper: Essential for seasoning the potato layers throughout the gratin.

See the recipe card at the bottom of the post for exact quantities and full instructions.

Ingredients for potatoes au gratin with gruyere cheese.

How to Make Potatoes Au Gratin

Slice and layer the potatoes. Preheat the oven to 375°F (190°C) and generously butter a 9×13-inch baking dish. Slice the potatoes evenly, about ⅛ inch thick, then arrange the first layer in the dish, slightly overlapping the slices. Season with salt and pepper.
Prepare the cream mixture. Add the heavy cream, whole milk, garlic and nutmeg to a saucepan. Warm gently over medium heat until hot, but do not let it boil. Remove from the heat and stir in half of the fresh thyme.

Layer the gratin. Sprinkle one-third of the Gruyère and Parmesan over the first layer of potatoes, followed by one-third of the warm cream mixture. Repeat the potato, seasoning, cheese and cream layers twice more, finishing with cream and a generous layer of cheese.
Bake until tender and golden. Cover the baking dish tightly with foil and bake for 40 minutes. Remove the foil and bake for another 20–30 minutes, until the potatoes are completely tender and the top is bubbling and deeply golden. Sprinkle with the remaining fresh thyme.
Rest before serving. Let the potatoes au gratin rest for 10 minutes before serving. This gives the starch-thickened cream time to settle around the potatoes and makes the gratin easier to serve.

Chef’s Guide: Expert Tips

Drawing on a decade of experience in Michelin-starred kitchens and Cordon Bleu training, I have compiled my top tips for recipe success.

Slice the potatoes evenly: Aim for slices about ⅛ inch (3 mm) thick. A mandoline is ideal because uniformly thin slices cook at the same rate.
Don’t rinse the potatoes: The starch clinging to the freshly cut potatoes helps naturally thicken the cream as the gratin bakes.
Warm the cream, but don’t boil it: Gently heating the cream mixture helps infuse it with the garlic, thyme and nutmeg. It only needs to become hot; there’s no need to bring it to a boil.
Season every potato layer: Potatoes need plenty of seasoning. A little salt and pepper as you build each layer gives you a much better-seasoned gratin than relying on the cheese and cream alone.
Add the cream as you layer: Dividing the cream between the layers helps it distribute evenly throughout the dish rather than simply pouring everything over the top.
Keep it covered initially: The foil traps steam, helping the raw potato slices become tender before the top gets too dark. Removing the foil for the final 20–30 minutes allows the cheese to become bubbling and golden.
Check the center, not just the top: A beautifully browned gratin isn’t necessarily cooked through. Insert a thin knife into the center; it should slide through the potato layers with almost no resistance.
Rest for 10 minutes: This isn’t just about cooling it down. As the gratin rests, the potato starch and cream settle and thicken, giving you creamy, cohesive layers rather than cream running out across the plate.

Storing, Reheating & Make-Ahead

Fridge: Let the potatoes au gratin cool completely, then cover the baking dish or transfer leftovers to an airtight container. Refrigerate for up to 3–4 days.
Reheating: For the best texture, cover with foil and reheat in a 350°F (175°C) oven until hot throughout, removing the foil for the last few minutes to crisp the top again. Individual portions can be reheated in the microwave, although the topping will be softer.
Make ahead: Assemble the gratin as directed, cover tightly and refrigerate for up to 24 hours before baking. Let the dish sit at room temperature while the oven preheats, then bake as directed. Because you’re starting with a chilled gratin, it may need a little extra time in the oven; check that the center is completely tender rather than relying solely on the stated baking time.
Freezing: I don’t recommend freezing this gratin. Potatoes and dairy-based sauces can both change texture after freezing and thawing, so for the best creamy texture, make it fresh or prepare it a day ahead and refrigerate it.

FAQs

What are the best potatoes for potatoes au gratin?

Yukon Gold potatoes are ideal because they have a naturally creamy texture while still holding their shape as they bake. Russet potatoes also work well and release more starch, which helps thicken the cream.

Why are my potatoes au gratin still hard?

The potato slices may be too thick or uneven, or the gratin simply needs longer in the oven. Slice the potatoes about ⅛ inch (3 mm) thick and test the center with a thin knife before removing the dish from the oven. It should slide through the layers with almost no resistance.

Why is my potatoes au gratin watery?

The gratin may need more baking time or may have been served too quickly after coming out of the oven. The starch released by the potatoes thickens the cream as it cooks, and the sauce continues to settle as the gratin rests. Give it the full 10-minute rest before serving.

Can I make potatoes au gratin ahead of time?

Yes. Assemble the entire gratin, cover it tightly and refrigerate for up to 24 hours before baking. Let it sit at room temperature while the oven preheats, then bake as directed, allowing a little extra time if needed because the dish is starting cold.

Easy Classic Potatoes Au Gratin

Thinly sliced potatoes layered with Gruyère and Parmesan and baked in a garlic, thyme, and nutmeg-infused cream sauce until tender, bubbling, and golden.

4.41 from 10 votes

Print Pin Rate

Prep Time: 20

Cook Time: 1 10

Total Time: 1 30

Servings: Servings

Author: Deborah Rainford

Ingredients

2½ pounds (1 ¼ kg) Yukon Gold or Russet potatoes, thinly sliced
2 cups (475 ml) heavy cream
1 cup (250 ml) whole milk
3 cloves garlic, minced
1½ cups (170 g) grated Gruyère cheese
½ cup (50 g) grated Parmesan cheese
2 tablespoons fresh thyme leaves, finely chopped, divided
¼ teaspoon freshly grated nutmeg
Salt and freshly ground black pepper, to taste
Butter, for greasing the baking dish

Instructions

Preheat and prepare: Preheat the oven to 375°F (190°C). Generously butter a 9×13-inch baking dish.
Slice the potatoes: Using a mandoline or sharp knife, slice the potatoes evenly, about ⅛ inch (3 mm) thick. Do not rinse the sliced potatoes.
Prepare the cream mixture: Combine the heavy cream, whole milk, garlic, and nutmeg in a medium saucepan. Warm over medium heat until hot but not boiling. Remove from the heat and stir in half of the thyme.
Start layering: Arrange one-third of the potato slices in the bottom of the prepared baking dish, slightly overlapping them. Season lightly with salt and black pepper.
Add the cheese and cream: Sprinkle one-third of the Gruyère and Parmesan over the potatoes, then pour one-third of the warm cream mixture evenly over the layer.
Repeat the layers: Repeat the potatoes, seasoning, cheese, and cream twice more, finishing with the remaining cream and a generous layer of cheese on top.
Bake covered: Cover the baking dish tightly with aluminum foil and bake for 40 minutes.
Brown the top: Remove the foil and continue baking for 20–30 minutes, until the top is bubbling and deeply golden and a thin knife slides easily through the potatoes in the center of the dish.
Rest and serve: Sprinkle with the remaining fresh thyme and let the gratin rest for 10 minutes before serving.

Notes

Potatoes: Yukon Gold potatoes give the gratin a buttery, creamy texture, while Russets are starchier and produce a softer texture. Whichever you choose, slice them evenly to about ⅛ inch (3 mm) thick.
Don’t rinse the potatoes: The starch on the cut potatoes helps naturally thicken the cream as the gratin bakes.
Check for doneness: Use a thin knife to test the center rather than relying on baking time alone. It should pass easily through the potato layers without resistance.
Rest before serving: Let the gratin stand for 10 minutes after baking. This gives the cream and potato starch time to settle and thicken around the layers.
Make ahead: Assemble the gratin up to 24 hours ahead, cover tightly, and refrigerate. Press plastic wrap directly against the surface before covering to help prevent the exposed potatoes from discoloring. The potatoes will absorb some of the cream overnight; don’t add extra cream. Remove the plastic wrap before baking and allow a little extra baking time because the dish will be starting cold.
Storage: Refrigerate leftovers in an airtight container or tightly covered baking dish for 3–4 days. Reheat covered in a 350°F (175°C) oven until hot throughout, uncovering for the last few minutes to re-crisp the top.

Nutrition

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Meet the Chef!

Hi, I’m Debs, a Cordon Bleu-trained chef and recipe developer. I help you get incredible dinners on the table fast with fool-proof recipes, step-by-step instructions, and tips and tricks I’ve learned over a 10-year career in professional kitchens.

4.41 from 10 votes (5 ratings without comment)

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