'Heaven in a casserole dish': Potatoes au gratin are the must-make Easter side

If there's one dish I'll never skip at a holiday dinner, it's potatoes au gratin. Infused with garlic and thyme and layered with Gruyère and Parmesan, a bubbling dish of these rich and creamy potatoes always takes center stage. This recipe takes a little time, but most of this is hands-off waiting, so you can multitask as you please. And if you don’t have that time on the day you want to actually serve it, you can even make it in advance! Mashed potatoes may get the majority of the spotlight, but if you really want to impress your guests, this is the side dish to make.

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How To Make Potatoes Au Gratin

INGREDIENTS

• Yukon Gold Potatoes: While many recipes call for the more starchy russet potato, I prefer Yukon Golds. They have a medium starch content that still provides plenty of thickening power—and they offer a creamy buttery texture that just takes this dish over the top.
• Heavy Cream & Milk: I find that a 1:1 ratio of heavy cream and milk provides the perfect creamy base for this gratin. If you have half-and-half, you can just use that!
• Shallot: The sweeter baby sister of onions, shallot is perfect for infusing a mild onion vibe into the milk and cream.
• Garlic: Crushed garlic will infuse better into the cream than whole garlic cloves, while still remaining easy to strain out.
• Thyme: Fresh is definitely the way to go here. If you only have dried, I’d recommend leaving it out of the steeped milk and cream mixture and only sprinkling 1/4 tsp. between each gratin layer.
• Kosher Salt: I developed this recipe using Diamond Crystal kosher salt. If you have Morton or need to use table salt, I highly recommend cutting the salt quantity in half, since these salts are denser by volume than Diamond Crystal kosher salt.
• Gruyère: Cheese is traditional in potatoes au gratin (in fact, it’s what differentiates it from scalloped potatoes). With its rich nuttiness and slight funk, Gruyère brings the perfect balance to all the rich creaminess.
• Parmesan: A little Parmesan adds pops of salt and acidity to balance out the Gruyère. Freshly grated from a block is always best!

STEP-BY-STEP INSTRUCTIONS

In a medium pot, combine the quartered shallot, crushed garlic, whole thyme sprigs, and some cream and milk. Cover and set the pot over medium-high heat. Bring to a simmer, stirring occasionally to make sure the bottom isn’t scorching. Once the mixture is simmering, remove the pan from the heat, cover, and let it sit untouched for 30 minutes so the aromatics can infuse into the cream and milk.

Potatoes Au Gratin

In the meantime, butter a 13" x 9" baking dish and preheat the oven to 350° with the rack in the middle position. While the cream and milk are infusing, prep the potatoes by peeling and slicing them into 1/8" slices. I prefer using a small handheld mandoline for this: it’s the best tool for getting super-even, super-thin slices. Mandolines can be intimidating for some people, but as long as you use the guard, you should be just fine. There’s no need to be concerned about the potatoes oxidizing here: One huge perk of Yukon Gold potatoes is that they don’t oxidize like russets do. Simply transfer the potatoes to a bowl and keep them uncovered at room temperature until ready to use.

Potatoes Au Gratin

Once the cream and milk are done infusing, strain the mixture through a fine mesh strainer into a bowl (you can discard the shallot, garlic, and thyme stalks). Return the cream mixture to the pot and add the salt and the potatoes. Bring everything to a simmer over medium-high heat, then cook, stirring occasionally, until the potato slices are fork-tender, which should take 4 to 5 minutes. This simmering step kick-starts the cooking of the potatoes, but it also activates their starch, drawing it out and using it to thicken the sauce. By the end of the 5 minutes, you will notice the cream mixture has thickened considerably.

Potatoes Au Gratin

Transfer a third of the potatoes and cream mixture to the prepared baking dish, then sprinkle with a third each of the Gruyère, Parmesan, and fresh thyme leaves. Repeat these layers once, then finish by topping with the remaining potatoes, Gruyère, and Parmesan. Hold on to the thyme for now—you’ll sprinkle it over the top after it bakes.

Bake the gratin, uncovered, for 40 to 50 minutes, or until it’s bubbling and golden brown on top. Wait about 5 minutes before topping with thyme and serving!

Potatoes Au Gratin

The full list of ingredients and instructions can be found in the recipe below.

Recipe Tips

• Use a mandoline: A mandoline is your best friend when it comes to slicing potatoes for gratin. It cuts the prep time in half, and delivers perfectly sliced potatoes—which, in addition to looking nicer, will also cook more evenly. Many people are skittish about them, but as long as you use the guard, you should be just fine.
• Don’t be afraid of the salt: A whole tablespoon might seem like a ton, but it’s not a misprint. Potatoes absolutely DRINK salt, and the richness of the heavy cream and whole milk demand it too. Please note though, that if you’re using table salt or Morton kosher (which are saltier by volume), you should decrease the salt by about half.
• Leave some pretty potatoes for the top: For the prettiest potato gratin, pick out some super gorgeous potato pieces and set them aside for the top layer; otherwise, you’ll end up using the potatoes at the bottom of the pot for the very top of your gratin—and often, they’re not the prettiest.

Potatoes Au Gratin Variations

• Potato Gratin Bundles: If you're looking for a fun, personal presentation for these potatoes, then these bundles are the perfect spin on this classic side dish.
• Potato Gratin Stacks: Not only are these an adorable, appetizer-sized variation, but these stacks have one important upgrade—crispy pieces of bacon.

Make Ahead & Storage

If you’d like to make these potatoes in advance, cook the entire dish all the way through, then let it cool completely before covering and refrigerating it for up to 3 days. When you’d like to serve, reheat them, covered, in a 350° oven. Smaller leftover portions can be stored in an airtight container and reheated in the microwave.

Potatoes au gratin

Potatoes au gratin

Made This?

Rate and review it in the comments below!

Yields: 8 servings

Prep Time: 15 minutes

Total Time: 1 hour 45 minutes

Ingredients

• 1

  shallot, peeled, quartered

• 4

  garlic cloves, peeled, smashed

• 2 c.

  heavy cream

• 2 c.

  whole milk

• 2

  to 3 thyme sprigs, plus 1 1/2 tsp. fresh thyme leaves, divided

• Unsalted butter, for greasing

• 2 1/2 lb.

  Yukon Gold potatoes (about 5 medium)

• 1 tbsp.

  kosher salt

• 6 oz.

  Gruyère, coarsely shredded (about 1 1/2 cups), divided

• 2 oz.

  Parmesan, finely shredded (about 1 cup), divided

Directions

1. In a large pot over medium-high heat, bring shallot, garlic, cream, milk, and thyme sprigs to a simmer. Remove from heat, cover, and let steep 30 minutes.
2. Meanwhile, arrange a rack in center of oven; preheat to 350°. Grease a 13" x 9" baking dish with butter. Peel and slice potatoes into 1/8"-thick slices (a small handheld mandoline works well for this).
3. Strain cream mixture through a fine-mesh sieve into a large bowl, then return to pot; discard solids. Stir in salt, then add potatoes. Bring to a simmer and cook over medium-high heat, stirring occasionally, until just tender, 4 to 5 minutes.
4. Pour one-third of potato mixture into prepared dish. Top with one-third of Gruyère and one-third of Parmesan. Sprinkle with 1/2 tsp. thyme leaves. Repeat the layers once more. Finish by topping with remaining potato mixture (making sure to add all the cream), Gruyère, and Parmesan; reserve remaining 1/2 tsp. thyme.
5. Bake potato gratin until golden brown on top and bubbling, 40 to 50 minutes. Top with reserved thyme.