Recipes | Side Dishes

Classic Potato Gratin – Lactose Free – Low FODMAP


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Low FODMAP Potato Gratin

What do I crave alongside my roast beef, leg of lamb or baked ham? Potato Gratin, which is why we figured it was about time that we added one to our line-up.

And it goes great alongside a roast chicken or turkey, as well.

potato gratin in a casserole dish in the background; on a plate in the foreground

Here it is in all of its dairy-rich, starchy glory. Potato gratin often includes garlic; ours does not, but you won’t miss it, especially if you include the optional thyme and nutmeg, which we think add a very nice touch.

If you are a purist, leave them out.

overhead shot of potato gratin in an oval casserole

We Love Lactose-Free Half-and-Half

Many potato gratin recipes use heavy cream. We opted for lactose-free half-and-half for a lighter version, but don’t get us wrong, this is still quite rich and small servings are recommended.

Please read our article, All About Cream & FODMAPs to learn what “half-and-half” might be called in your part of the world.

One Potato, Two Potato – MANY Potatoes

You will be using a full 2 pounds (910 g) of potatoes for this dish, the starchier the better.

You could use Yukon Golds, which lend a golden color and keep their shape better, but we like the texture of the meltingly starchy russet-type baking potatoes.

Also, you can slice the potatoes by hand, but if you have a mandoline, it works wonders here for nice, even, thin slices (see Tips).

potato gratin on a white plate with a fork alongside

Techniques vary for this dish. Some recipes have you gently boil the cream first to reduce it a little, but the danger here is that it can break.

Other recipes have you layer raw potatoes right in the casserole dish and top with hot cream. I like to simmer the potatoes briefly in the half-and-half on top of the stove.

It just seems to bring the potatoes and dairy together in a fantastic way that ultimately gives you a super creamy, silky potato gratin.

Note from Robin: Make sure you make a large casserole dish of these. They are AMAZING as leftovers. I put mine into a cast iron pan in a 350°F/180°C oven for 20 minutes and they came out crispy, and creamy and seriously yummy.

So easy to add alongside eggs and bacon, or a salad and you have a meal.

Check out our version with mushrooms as well. Oyster mushrooms are low FODMAP and we put them to great use in our Low FODMAP Potato Cheese Gratin with Mushrooms.

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overhead shot of potato gratin in an oval casserole
3.79 from 33 votes

Classic Potato Gratin

Our Classic Potato Gratin is low FODMAP and features lactose-free half-and-half.

Makes: 14 Servings
Prep Time: 15 minutes
Cook Time: 40 minutes
Total Time: 55 minutes
Author: Dédé Wilson


  • 1/2 tablespoon unsalted butter
  • 2 pounds (910 g) russet potatoes, peeled
  • 3 cups (720 ml) lactose-free half-and-half, such as Organic Valley
  • 1 teaspoon kosher salt
  • Freshly ground black pepper
  • 1/4 teaspoon fresh thyme, optional
  • Pinch freshly ground nutmeg, optional
  • 1/4 pound (115 g) Gruyere cheese, grated (see Tips)


  1. Position rack in middle of oven. Preheat the oven to 400°F/200°C. Use butter to coat the inside of a 3-quart (2.8 L) shallow casserole dish and set aside.
  2. Cut the potatoes into very thin 1/8-inch (3 mm) slices using a very sharp knife or a mandoline (see Tips). Keep them in rounds, if possible.
  3. Place the potatoes in a wide heavy saucepan (I use a 3-quart/2.8 L) and add the half-and-half, salt, a generous amount of pepper and thyme and/or nutmeg, if using. Bring to a vigorous simmer over medium heat, shaking the pan occasionally, and simmer for 3 minutes.
  4. Carefully pour the mixture into prepared casserole dish. Use a silicone spatula to gently coax the potatoes and liquid into an even layer. Sprinkle the cheese evenly over the top.
  5. Bake for about 35 to 45 minutes or until the potatoes are tender when pierced with a knife and the top is golden and bubbling. The mixture might look a little loose, but don’t worry, it will firm up upon cooling. Place casserole on a rack and cool for at least 15 minutes to allow the gratin to achieve its maximum potato perfection. Serve warm or even at room temperature.



  • Cutting the potatoes as thin as recommended is a very important step. Pull out a ruler if you have to, to make sure they are thin enough or they will not cook properly. The beauty of a mandoline is that you can set it to the desired thickness and just got to town, knowing that all of your potatoes will be perfectly cut. You could also use a food processor fitted with the appropriate sized slicing disc.
  • You could play around with other types of cheese. Emmental or Comté would be good alternative choices. Plain Swiss doesn’t have enough sharpness, in my opinion, but use your own palate as a guide.
Course: Side Dish
Cuisine: American, French


Calories: 152kcal | Carbohydrates: 14g | Protein: 5g | Fat: 9g | Saturated Fat: 1g | Sodium: 215mg | Potassium: 270mg | Fiber: 1g | Sugar: 1g | Vitamin C: 3.7mg | Calcium: 8mg | Iron: 0.6mg

All nutritional information is based on third-party calculations and should be considered estimates. Actual nutritional content will vary with brands used, measuring methods, portion sizes and more. For a more detailed explanation, please read our article Understanding The Nutrition Panel Within Our Recipes.