Why You’ll Love This Recipe

I love this recipe because it looks impressive but is surprisingly simple to make. I appreciate how the garlic, shallot, and thyme infuse deeply into the cream, giving every bite incredible flavor. I also enjoy how the potatoes partially cook in the cream before baking, creating a perfectly thick, silky sauce and guaranteeing tender layers once baked.

Ingredients

(Note: All ingredient amounts are listed in the recipe card below.)

1 shallot, peeled, quartered
4 garlic cloves, peeled, smashed
2 cups heavy cream
2 cups 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. I place the shallot, garlic, cream, milk, and thyme sprigs in a large pot over medium-high heat and bring it to a simmer. I remove it from the heat, cover it, and let it steep for 30 minutes.

2. I preheat the oven to 350°F and grease a 13″ x 9″ baking dish with butter. I peel the potatoes and slice them into 1/8-inch slices, using a mandoline for even cuts.

3. I strain the cream mixture through a fine-mesh sieve, discard the solids, return the liquid to the pot, stir in the salt, and add the sliced potatoes. I bring it to a simmer and cook for 4 to 5 minutes, stirring occasionally, until the potatoes are just tender.

4. I transfer one-third of the potato mixture to the baking dish, top it with one-third of the Gruyère and Parmesan, and sprinkle with 1/2 teaspoon of thyme leaves. I repeat the layers once more, then finish with the remaining potatoes, all the cream, the rest of the Gruyère and Parmesan, and reserve 1/2 teaspoon of thyme.

5. I bake the gratin for 40 to 50 minutes, or until bubbling and golden brown. I top it with the reserved thyme before serving.

Servings and Timing

Servings: 8
Prep Time: 15 minutes
Total Time: 1 hour 45 minutes

Variations

I sometimes add caramelized onions between the layers for extra sweetness.
I use a mix of Gruyère and sharp cheddar when I want a bolder cheese flavor.
I sprinkle a bit of nutmeg into the cream for warmth.

Storage/Reheating

I refrigerate leftovers for up to 3 days, keeping them tightly covered.
I reheat the gratin in the oven at 350°F, covered, until warmed through.
I reheat smaller portions in the microwave, though the oven keeps the top crispier.
I make the whole dish ahead, cool it completely, and refrigerate it to reheat later.

FAQs

Can I use russet potatoes instead of Yukon Gold?

I can, but Yukon Golds give a creamier texture and don’t oxidize as quickly.

Do I have to use a mandoline?

I don’t, but a mandoline makes slicing easier and ensures even cooking.

Can I use half-and-half instead of cream and milk?

I can substitute an equal amount of half-and-half.

Why is my gratin watery?

I make sure to simmer the potatoes in the cream so their starch thickens the sauce.

Can I assemble it ahead but bake later?

I prefer baking it fully, then reheating, to avoid discoloration and texture change.

Can I add more cheese?

I can easily increase the cheese amounts for a richer gratin.

How do I prevent the top from overbrowning?

I tent the dish with foil if it browns too quickly.

Can I freeze potatoes au gratin?

I avoid freezing because the texture of the potatoes can become grainy.

How thin do the potatoes need to be?

About 1/8 inch ensures even layering and tender results.

Can I reduce the salt?

I can, but I keep in mind that potatoes absorb a lot of seasoning.

Conclusion

I love how this potatoes au gratin recipe turns simple ingredients into a luxurious, golden-topped dish. The infused cream, tender potato layers, and cheesy finish make it a standout side that feels classic, comforting, and deeply satisfying every time I make it.