French Potato and Onion Gratin

potato gratin with thyme

French Potato and Onion Gratin ~ this quintessential fall side dish of potatoes and onions cooked up in a simple cheesy cream sauce is easy enough for a family dinner, but indulgent enough for any holiday table.

It’s technically a side dish, but I love this gratin so much I often have it on its own for dinner. A little Chardonnay and a few leaves of crisp lettuce and I’m a happy girl  Super cozy, too. I first learned to do gratins from Ina Garten, and she is still my model for utter simplicity and authentic French style. These simple baked dishes are nothing but thinly sliced vegetables layered up with cheese and some sort of milk or cream. Sometimes butter… always fresh herbs.

I got mildly obsessed with this gratin last week, and made it few times in a row, each time with a different herb. One delicious discovery was fresh marjoram. I bought a small bunch when I saw it at my supermarket, and then it sat on the counter in a little glass of water for about a week, and by the time I got around to using it, it had dried out. Even in dried form it was amazing. If you can’t find marjoram, ask your produce manager to get it in for you. But here are some other fresh herbs that give this gratin a similar French countryside vibe ~

  • thyme
  • oregano
  • rosemary (be sure to finely mince it)

One dry herb mix I would recommend if you don’t have the above fresh herbs is herbes de Provence. It’s a mix of savory, marjoram, rosemary, thyme, oregano, and sometimes lavender and you should be able to find it right in your supermarket spice aisle.

In fall you can find all sorts of fresh herbs in the supermarket that you don’t see during the rest of the year as the country gears up for holiday cooking. It’s a great time to experiment with new flavors!

My biggest challenge with gratins is making sure to cook them long enough. I often think I’ve done it perfectly, only to take that first forkful and have it be not quite tender enough. This one really takes at least an hour and a half for the potatoes to be totally tender, probably a little longer, which is completely counter intuitive since they’re so paper thin. But as long as you give it enough time, it’s going to be delicious.

TIP: Check for doneness by inserting a small sharp knife down into the potatoes. If it slides in super easily, it’s done. If you feel the slightest resistance, keep cooking!! Use foil if it seems to be browning too quickly.

At precisely the 28 minute mark your kitchen will start to smell like a French farmhouse

Gratins can be made with all sorts of veggies, like cauliflower, zucchini, even winter squash. They’re super easy to put together, and can definitely be assembled ahead of time and baked off later.

As for the cheese, I like to use a good sharp white cheddar, but if you’re feeling spendy, go for Gruyere! Be aware that whatever cheese you go for, this rustic French gratin doesn’t have a creamy sauce like you get in a macaroni and cheese. The cream and cheese cook together but don’t combine into a homogeneous sauce, that’s just the nature of the beast.

Ok, let’s dig in!

potato gratin with thyme
3.35 from 86 votes

Potato and Onion Gratin

French Potato and Onion Gratin ~ this quintessential fall side dish of potatoes and onions cooked up in a simple cheesy cream sauce is easy enough for a family dinner, but indulgent enough for any holiday table.
Course Side Dish
Cuisine French
Prep Time 20 minutes
Cook Time 1 hour 30 minutes
Yield 8 servings
Author Sue Moran


  • 2 russet baking potatoes washed and peeled
  • 1 medium onion
  • 1 tsp salt and fresh cracked black pepper to taste
  • 2 cups shredded sharp cheddar divided
  • 1 cup heavy cream divided
  • 3 Tbsp fresh marjoram oregano, or thyme leaves, plus for for garnish
  • 2 Tbsp butter cut in pieces


  • Set oven to 350F
  • Slice the peeled potatoes into 1/8 inch slices with a mandoline slicer.
  • Slice the onions the same way. Cut the onion slices into quarters so there will be no long stringy pieces.
  • In a very large bowl add the onions, potato slices, 3/4 cup of the cream, the fresh herbs, and 1 1/2 cups of the cheese ~ mix well with clean hands. Season with salt and cracked pepper. Separate the potato slices as best you can.
  • Pile the mixture into an 11-12 inch gratin dish. Arrange the potatoes evenly. Dot with the butter.
  • Blend the remaining cheese and cream together
  • Dot the potatoes with the pieces of butter, and then top with the remaining cheese and cream.
  • Cover loosely with foil and bake for about 90 minutes, or until browned and bubbling, and you can easily pierce the potatoes with the tip of a sharp knife. Remove the foil for the last 1/2 hour of baking.
  • Run under the broiler at the end if you want more browning.
The nutritional information for recipes on this site is provided as a courtesy and although tries to provide accurate nutritional information, these figures are only estimates.

Make this French potato and onion gratin your own ~

  • Ina Garten uses very thinly sliced fennel in place of the onions.
  • You can use evaporated milk instead of cream to cut down on calories, but the sauce will be thinner and more watery.
  • If you want a creamy bechamel style sauce, make it separately, blend in the cheese, and then combine with the potatoes et al before cooking.


Don’t forget to pin this French Potato and Onion Gratin!

French Potato and Onion Gratin pin


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    Please rate this recipe!

  • Reply
    November 20, 2019 at 8:38 am

    Oooo, this looks yummy, but I am with Patricia, can you provide an approximate weight of the taters we have russets that range from 4 inches long to over 7 inches…

    • Reply
      November 20, 2019 at 8:45 am

      Average russets weigh 6-8 ounces, if that helps!

  • Reply
    November 10, 2019 at 8:11 am

    Russet potatoes come in so many sizes! Would you give a weight option, please?

  • Reply
    October 17, 2019 at 10:39 am

    how much herbes de provence would I use? Thanks, can’t wait to try this.

    • Reply
      October 17, 2019 at 1:30 pm

      Dried herbs are more pungent than fresh, so I might try a couple of teaspoons and taste.

  • Reply
    February 13, 2019 at 9:35 pm

    Would it be a problem if I used red potatoes instead of russet baking potatoes? Thank you for the quick reply.

    • Reply
      February 14, 2019 at 7:01 am

      It won’t be a problem, but the texture of baked red potatoes is a little different, not as soft and creamy, but more firm than russets.

  • Reply
    December 16, 2017 at 2:01 pm

    what do you think of using half white cheddar and half Gruyere? Good idea or bad?

    • Reply
      December 16, 2017 at 2:08 pm

      Gruyere is never a bad idea 😉 I think it would be great.

  • Reply
    November 22, 2017 at 12:55 pm

    Can you prepare this and keep it in the fridge, then bake it in the oven the next day or should you prepare it the same day you want to bake it? (Using for a Thanksgiving side dish.) Thank you!

    • Reply
      November 22, 2017 at 12:59 pm

      I think you should be able to assemble it the day before, Amy, and I would take it out of the refrigerator early to allow it come to room temperature if possible, so the baking time will be the same. Happy Thanksgiving!

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