Perfect Classic Potatoes Au Gratin (with Poblanos)

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.

Jump to Recipe

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. I love using poblanos in a pasta sauce and even in Mexican Spaghetti Soup (Sopa de Fideo Verde).

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. And if you want a potato dish for Passover, make this Passover Potato Kugel.

❤️ 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.

---

👩‍🍳 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.

😋 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:

1. 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.
2. 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.
3. 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.
4. 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:

1. 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.
2. 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.