This classic potato gratin recipe is switched up with added roasted poblano peppers. Thinly sliced potatoes are layered with cheese and peppers making this a special casserole.
The post includes tips for choosing the best kind of potatoes, cheeses, and how to make your au gratin even creamier.
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Jump to:
- ❤️ Why you'll love this recipe
- 🧅 Main Ingredients + Notes
- 👩🍳 What are the best potatoes for au gratin?
- 🤷♀️ What's the best cheese for potatoes au gratin?
- 👩🍳 Must I use heavy cream in potato gratins?
- 🔪 Recommended Equipment
- 😋 How to build flavor in your au gratin
- 🤷♀️ Potatoes Au Gratin FAQ
- Classic Potato Gratin (with Poblanos)
First of all, yes I know a classic potatoes au gratin doesn't include roasted poblanos.
But I swear, everything else in this recipe is totally classic. If you object to the poblano, just eliminate it without making any other changes. I love roasted poblanos and add them to lots of dishes for some heat. I add it to this vegetarian tetrazzini and sometimes to my stuffed delicata squash in place of Serrano peppers.
This is a perfect side dish for Thanksgiving, Christmas, and Easter dinner.
❤️ Why you'll love this recipe
- Perfect comfort food - between the potatoes, the cream, and the cheese, a casserole like this defines comfort food.
- Crowd pleaser - perfect for any crowd and a great potluck dish.
- Assemble ahead - if you'll be rushed for time on the day you plan to serve it, assemble this au gratin the day before, cover it with plastic, and refrigerate. Bring to room temperature while the oven pre-heats.
🧅 Main Ingredients + Notes
The secret to faster and easier meals often lies in the ingredients. For example, store-bought items and ingredients you make ahead and store in the refrigerator (or freezer) can turn a 60-minute recipe into a 30-minutes meal or less.
For the all of the ingredients, measurements and directions, go to the Recipe Card at the bottom of this post.
- Garlic - use either fresh garlic or store-bought garlic paste.
- Shallot
- Heavy cream
- Whole milk
- Bouillon cube or paste - I highly recommend Better Than Bouillon. I use the roasted vegetable paste flavor.
- Dijon mustard
- Fresh thyme - dried thyme is ok, but not as good for infusing flavor into the cream.
- Poblano pepper - you can substitute canned Hatch chilies or other green chilies, or purchase frozen roasted and chopped Hatch chilies. I often have this in my freezer.
- Yukon potatoes - see in a below section on why Yukons are better than russets in an au gratin casserole.
- Swiss cheese - I use Gruyere, but any Swiss cheese works great.
- Parmesan cheese
- Breadcrumbs - I always have a stash of cheater Panko gremolata breadcrumbs made with Panko on hand.
👩🍳 What are the best potatoes for au gratin?
The two most popular choices are russets and Yukon golds. And the final decision balances creaminess against the ability of the potatoes to hold their shape when baked. In the end it's up to you which is more important.
Russet potatoes have the highest starch content. They cook up less dense than Yukon golds, and don't hold their shape as well. And this is what's important for the ultimate creamy potatoes au gratin. Russets break down a little into the sauce, making it creamier. Just be sure not to over bake a gratin using russets, as they can become mushy.
Pro tip: Russet potatoes absorb more liquid than Yukon golds. The recipe below is written for Yukons. If you choose to go with russets, add an additional ½ cup of heavy cream. And be sure to re-balance the seasoning.
Yukon Gold potatoes are the next step down in starch content. They hold their shape very well, including when scooped out onto plates. Since they hold their shape and don't partially disintegrate into the cream, these gratins aren't quite as creamy - although I admit they're plenty creamy for me. Many people see Yukon golds as the best overall combination.
Pro-tip: If you want to amp up the creaminess of a gratin using Yukon golds, add 1 tablespoon all-purpose flour to the cream mixture on the stove. This will thicken the sauce a bit more. Another tip is to add several thin pats of butter between each layer of potatoes.
And if you're wondering the best way to store potatoes, read this article on whether potatoes should be refrigerated or not.
🤷♀️ What's the best cheese for potatoes au gratin?
The traditional cheese used in potatoes au gratin is Gruyere. But feel free to mix it up with other cheeses, so long as they're good melting cheeses. I've used Monterey Jack Cheese with great success, and I've seen cheddar used as well.
I always like to add a little Parmigiano Reggiano cheese for a hint of sharpness to a cheesy creamy dish. If it's not available, you can use Pecorino Romano cheese instead.
Pro-tip: Grate your own cheese. Pre-grated cheese in plastic bags in the market includes cellulose which prevents the cheese from caking together. The cellulose dries the cheese and mutes its flavor.
👩🍳 Must I use heavy cream in potato gratins?
No. The purpose of using heavy cream is to create a thick sauce. Heavy cream thickens with heat.
However, you can use whole or (to some extent) 2% milk. But you'll need to thicken it by making a roux with flour as in this Spinach Madeline. Use 2 tablespoons of butter and 2 tablespoons of all-purpose flour.
Disclosure: This post may contain affiliate links to products and foods I use in my kitchen. This means that at no additional cost to you, I will earn a commission if you click through and make a purchase. To view my entire storefront of recommended kitchen tools and equipment, check out my shop on Amazon.
🔪 Recommended Equipment
- 9" X 13" baking dish
- Chef's knife
- Medium pot
- Hand-held mandolin - for evenly and quickly slicing the potatoes
- Cheese grater
😋 How to build flavor in your au gratin
I've yet to meet a potato au gratin I haven't loved. But my favorites are ones with a lot of flavor in the sauce.
I do this a few ways:
- I add a scoop of Better Than Bouillion paste plus mustard to the cream and milk mixture on the stove. I used the Roasted Vegetable Better Than Bouillion Paste, but if you don't follow a vegetarian diet, the chicken flavored Better Than Bouillon works well in this recipe.
- Next, I steep herbs, such as thyme, in the cream mixture. I've also used sage with great success, but because its flavor is stronger, I don't need nearly as much.
- Finally, I reduce the cream mixture over a low simmer, and allow it to cool before removing the herbs from the pan. This intensifies the flavors and infuses the herbs just the right amount in the sauce.
- If you want a little more spice and heat, to go with the poblano pepper, add a sprinkling of this chipotle spice rub between each layer of potatoes. Or swap out the herbs for a dried chipotle pepper that are steeped in the cream on the stove.
🤷♀️ Potatoes Au Gratin FAQ
Can I make this dish ahead?
Yes. I've done this a couple different ways:
- Make the entire gratin ahead, including baking, except adding the breadcrumbs. Reheat with the breadcrumbs on top. If you choose this make-ahead path, add an additional ¼ cup of heavy cream to the pot when simmering with the herbs. The potatoes will absorb some of the liquid in the refrigerator. If you don't add extra cream, the gratin will be a bit dry.
- Make the gratin up to the point where you bake it off. Cover it, and place in the refrigerator. As a note, the baking time will be extended if you place the gratin in the oven while it's still cold. I recommend adding the extra ¼ cup liquid to the cream sauce as the raw potatoes will absorb some of the cream in the refrigerator.
Can I freeze this dish?
I don't freeze dishes with cream, as the risk of it separating upon thawing is high.
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Classic Potato Gratin (with Poblanos)
Equipment
- sharp chef's knife
- medium pot
Ingredients
- 2 tablespoons unsalted butter, room temperature, divided
- 1 medium shallot, peeled and thinly sliced
- 1 tablespoon garlic paste, or 3 garlic cloves, peeled, smashed and minced
- 2 cups heavy cream
- ½ cup whole milk
- 1 teaspoon Better Than Bouillon paste
- 1 teaspoon dijon mustard
- ½ teaspoon kosher salt, or ¼ teaspoon table salt
- ¼ teaspoon freshly ground black pepper
- 10 sprigs fresh thyme
- 1 poblano pepper
- 4 pounds Yukon potatoes, unpeeled
- 3 ounces grated Gruyère cheese, about 1 ¼ cup
- 1 ounce grated Parmesan, about ¼ cup
- 2 tablespoons toasted breadcrumbs
Instructions
- Preheat the oven to 350˚F. Smear ½ tablespoon butter all over the inside of a 9" X 13" baking dish. Set aside.
- Melt the remaining butter in a medium pot over medium heat. Add the sliced shallot and garlic and sauté for 5 minutes.
- Stir in the cream and milk. Add the bouillion, mustard, salt, pepper and thyme sprigs. Simmer for 15 - 20 minutes, until reduced by ¼ cup. Let cool and remove the thyme.
- Roast the poblano pepper on a baking sheet under a broiler until the skin blisters, turning as needed. This should take about 15 minutes. Place in a jar or plastic bag. Seal and wait for 10 minutes. Remove the pepper and peel. Slice open, scrape out the seeds, and dice.
- Thinly slice the potatoes, approximately ⅛" thick. I use a hand-held mandolin, and set it on #2 setting.
- Arrange the potato slices like shingles on the bottom of the baking dish until the bottom is covered. Lightly salt and pepper the potatoes, and sprinkle ⅓ of the Gruyere cheese and ⅓ of the diced poblanos over the slices.
- Repeat for 2 more layers, finishing with the final ⅓ of the Gruyere and poblanos. Pour the cream reduction over the potatoes. Cover the baking dish tightly with foil. Bake for 60 - 75 minutes, until the potatoes are tender. If baking this at 5000-7000 feet, you may need to bake it for 75 - 85 minutes.
- Uncover, sprinkle with Parmesan and toasted breadcrumbs, if using. Bake for an additional 10 minutes.
- Serve piping hot.
mjskitchen
In organizing the freezer yesterday, I found a bag of roasted poblanos from last year's garden. What a fabulous way to use them! This looks so good.
The Wimpy Vegetarian
I make it quite a lot year round, and friends keep asking me for the recipe. But I'd never really written it down - hence the tweaking through the years. I finally took the time to do it. What a great idea to freeze roasted poblanos. Once they're roasted, do you need to do anything special before freezing them?
mjskitchen
We had a bumper crop of poblanos this year so I have many in the freezer; therefore, I'm excited about giving this recipe a try. I love au gratins but don't make them much and I'm not sure why. This looks delicious!
Pyrott
Not traditional when you add 3-4 extra ingredients including one so off base like peppers. Learn some terms like proper 'traditional' recipes.
The Wimpy Vegetarian
I actually learned quite a bit about proper "traditional" recipes in the professional culinary school I attended in San Francisco several years ago. The only ingredient that my school wouldn't have considered traditional is the peppers. We made a few variations of "traditional" potatoes au gratin, and hundreds of other recipes. In any culture, for any recipe, there is no one single version that the world would consider traditional. You may have missed it, but in the introduction at the very top of the page, as well as in the paragraph immediately under the table of contents (twice), I clearly state that the addition of peppers is my own twist, and is not considered traditional.
Judy McCarthy
PYRott. Traditional depends on where you are. I am in Santa Fe. Nothing strange about poblano peppers here!
The Wimpy Vegetarian
Lucky you! I love Santa Fe. I've been to the Farmers Market there when they were roasting poblanos, and I bought a few to stuff for dinner.
T Williams
This is one of the very best gratin recipes I've come across. Two of my kids said "Mom, this one is a keeper!" It certainly is. The only tweak I made was the addition of a pepper, as we love poblanos.
The Wimpy Vegetarian
Thank you so much for letting me know! I'm so glad you and your family enjoyed it!
Carolyn Melby
Ok I have way too many potato slices. Mine our closer together than in the picture. Isn't four pounds too much? Anyone else have the problem. I have a half bowl of sliced potatoes (from the mandolin sliced just as suggested.)
The Wimpy Vegetarian
That's a lot to have left over. What size is your casserole dish?
The Wimpy Vegetarian
I just measured the casserole dish I use for making this. It's 9" X 13" X 2.5" deep when measured on the inside of the dish. Could it be that your casserole dish is smaller than that?