Looking for a new side dish for your holiday spread? Give your cheesy potatoes a much-needed update with some nutty gruyere cheese, sauteéd portobello mushrooms, and a generous sprinkle of fresh thyme. This Potato & Mushroom Gratin will be a new family favorite that looks fancy but couldn't be easier to make.
Au gratin potatoes don't get the love they deserve. We took this Potato and Mushroom Gratin to another level and added some gruyere cheese along with some portobello mushrooms.
How can you resist a pile of tender potatoes baked in a creamy sauce filled with garlic and fresh thyme that pairs well with chicken, beef, or ham?
Short answer, you can't.
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Why you will love this potato gratin
✔️ It looks (and sounds) fancy but is super simple to make. After all, what even is a Gratin? Simply put, a gratin is a French dish that is made with cream and baked in a shallow pan with cheese or butter on top that gets nice and crispy.
✔️ It can be prepped ahead of time! This dish can be made early in the day or up to 24 hours ahead of time and refrigerated until ready to bake
✔️ It travels well! Are you in charge of the potatoes? This gratin tastes just as good when it has been baked earlier and reheated to eat with the rest of the holiday meal, (some may argue it tastes even better.)
Ingredients
You only need 6 ingredients to make this impressive French potato side dish.
Ingredient notes:
Potatoes: Russet potatoes are best for gratins as they keep their shape while they bake.
Heavy Cream: The fat in the cream gives you the rich flavor of the gratin. You can't swap half and half or milk and get the same results.
Cheese: Nutty gruyere pairs perfectly with the mushrooms and thyme. Don't have any on hand? You can use Swiss cheese instead.
Instructions
Making a potato gratin takes only a handful of steps.
Sauté the mushrooms in olive oil in a small pan until the moisture is released. In another small pan, heat the cream, garlic and thyme until heated but do not boil.
Slice the potatoes into very thin, even slices and place into baking dish. Pour the warm cream mixture over the top.
Sprinkle the swiss and gruyere cheese over the top of the potatoes. Add the sauteéd mushrooms on top of the cheese. Finally, sprinkle with parmesan cheese and bake.
FAQs
A gratin pan is a shallow oval baking dish that allows the ingredients to be spread in thin layers so you can have a large surface area on top that can get a nice browned crust when it is baked in the oven.
You can also use a 9 x13 pan, but check the potatoes after 35 minutes because your layers will be thinner.
There are a few kitchen tools that I will give up valuable storage space in my kitchen and a mandoline is one of them. There is NO better, faster way to get even thin-sliced potatoes than with a mandoline. I have an OXO mandoline slicer and I absolutely love it.
But please promise me that you will use the supplied holder to grip the potatoes. Your fingers will thank you for saving them from the sharp blades.
Yes, you can but there are some steps you need to follow to ensure your potatoes do not brown.
1. After you peel the potatoes, place them in a bowl of cold water when you are waiting to slice them.
2. As soon as they are sliced, place them in the baking dish and pour the warm cream mixture over the top, making sure to coat each potato slice.
3. Cover them with shredded cheese and mushrooms. When potatoes are exposed to air they will turn gray. Covering the top of the dish with the cheese and potatoes will prevent this.
4. Wrap them tightly with plastic wrap pressing down on top of dish to keep all air out. Refrigerate until ready to bake.
Absolutely. Simply follow the recipe as written and let cool completely before wrapping the baked Potato Gratin with foil and refrigerating.
When you are ready to reheat them, remove them from the refrigerator an hour before heating to allow them to come to room temperature.
Heat in a preheated 350°F oven for 30 minutes or until warmed through.
Expert Tips for the Best Potato Gratin
✘ Use the right potato. Stick with russet potatoes for this recipe as they do the best job of keeping their structure when baked in cream. Don't use Yukon Golds! Their water content is too high and the end result is a soupy mess.
✘ Slice the potatoes thinly. Thin and evenly sliced potatoes will give you the best result. All of the potatoes will cook evenly and give you the creamy texture you expect in a gratin.
✘ Heavy cream is a must. Ok, not really a must but to get the best potato and mushroom gratin you can, the heavy cream definitely makes a difference.
✘ Heat the cream, garlic, and thyme. This step seems like it would be a no-brainer to skip, but the fragrant flavor that cream gets when it is infused with garlic and thyme is a game changer.
More potato side dishes
We haven't met a potato dish that we didn't like. Try these Scalloped Potatoes or one of our other favorites below.
Did you make this recipe? We'd love to hear your thoughts!
Please rate the recipe and leave a comment below. Your feedback helps us and your fellow readers!
Recipe
Potato & Mushroom Gratin
Ingredients
- 5 medium russet potatoes, sliced thinly (⅛ inch thick)
- 1 tablespoon olive oil
- 8 ounces portabello mushrooms, sliced
- 1 ½ cups heavy cream
- 1 teaspoon thyme
- 1 teaspoon minced fresh garlic
- ½ cup shredded Swiss cheese
- 2 tablespoons grated parmesan cheese
- salt and pepper
- ½ cup shredded gruyere cheese
Instructions
- Preheat oven to 400°F degrees. Spray a 2 quart oval baking dish lightly with cooking spray and set aside.
- In a small skillet, add olive oil and mushrooms and heat on medium for 5-6 minutes to let mushrooms release moisture. Remove from heat and set aside.1 tablespoon olive oil, 8 ounces portabello mushrooms,
- In a small sauce pan, heat cream with garlic and thyme until it is heated through, but not boiling. Season with salt and pepper.1 ½ cups heavy cream, 1 teaspoon thyme, 1 teaspoon minced fresh garlic, salt and pepper
- Peel potatoes, cut into ⅛" slices and place in the baking dish.5 medium russet potatoes,
- Pour the warm cream sauce over the potatoes. Sprinkle the shredded cheeses on top and add the mushrooms. Sprinkle with parmesan cheese.
- Bake for 45 minutes or until browned and bubbly. Let gratin sit for 10 minutes before serving.
Notes
1. After you peel the potatoes, place them in a bowl of cold water when you are waiting to slice them.
2. As soon as they are sliced, place them in the baking dish and pour the cream over the top, making sure to coat each potato slice.
3. Cover them with shredded cheese and mushrooms. When potatoes are exposed to air they will turn gray. Covering the top of the dish with the cheese and potatoes will prevent this.
4. Wrap them tightly with plastic wrap pressing down on top of dish to keep all air out. Refrigerate until ready to bake.
- Simply follow the recipe as written and let cool completely before wrapping the baked Potato Gratin with foil and refrigerating.
- When you are ready to reheat the gratin, remove it from the refrigerator an hour before heating to allow it to come to room temperature.
- Reheat in a preheated 350°F oven for 30 minutes or until warmed through
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Nutrition
Nutrition info not guaranteed to be accurate.
So yummy! Great recipe. Made for a dinner party and it was a hit! Thank you again.
Ok, it's me again!! In picture # 5, it looks like I see some brown spots under the potatoes, which looks like that you tucked in some mushrooms in there, before you added all the mushrooms on top. Is that the case? I did make this for a test run, before Christmas dinner, & it is Amazing!! I will be needing to double the recipe for 10 adults, so I will be using 2 gratin pans. Just wanted to know if you tucked in some mushrooms in between the potatoes.
Hi Leslie, That is just some of the thyme that is the sauce when you pour it over, if you want to tuck some mushrooms in...go ahead! It works great! Glad you love it! Merry Christmas!
Will do!! Thanks! A Merry Christmas to you & your family!