Au Gratin Potatoes with Poblanos
Creamy, comforting potatoes au gratin with roasted poblanos for a gentle Mexican twist—simple prep, rich flavor, and mostly oven time.
There’s something deeply comforting about a casserole dish fresh from the oven. This one brings together cream, roasted poblanos, cheese, garlic, thyme, salt, and pepper—simple, familiar ingredients that come together into something truly special.
Thinly sliced potatoes are coated in a well-seasoned cream mixture, then layered into tight spirals that bake evenly and beautifully. The dish comes together in just a few steps, but the technique makes all the difference.
By the time it’s done, the casserole is rich and tender, with potatoes that melt into the cream, pockets of roasted poblanos throughout, and a golden, buttery top that pulls everything together.
It’s cozy, satisfying, and meant to be shared—just like the dishes we grew up with.
Ingredients
- Gold Potatoes – Naturally creamy with thin skins, they hold their shape well and don’t need peeling, adding both texture and fiber.
- Poblanos – Mildly smoky with gentle heat, roasted poblanos add depth and a subtle Mexican twist without overpowering the dish.
- Heavy Cream – The foundation of the gratin, creating a rich, silky sauce that coats every slice of potato.
- Gouda Cheese – Adds mellow sweetness and creaminess, melting smoothly into the sauce.
- Queso Oaxaca – Stretchy and buttery, it brings a familiar Mexican comfort and luxurious melt.
- Parmesan Cheese – Sharp and savory, it balances the richness and helps create a golden, flavorful crust.
- Garlic – Provides warmth and aroma.
- Fresh Thyme – Earthy and fragrant.
- Kosher Salt – Enhances all the flavors and ensures the potatoes are well seasoned throughout.
- Black Pepper – Adds gentle heat and balance without overpowering the cream.
- Unsalted Butter – Dotted on top, it enriches the gratin.
- Parsley – Fresh and bright, it finishes the dish with color and a clean, herbal note.
How to make Au Gratin Potatoes with Poblanos
Here’s a brief rundown of the main steps for making this recipe. For full, detailed instructions and exact measurements, head to the recipe card below.
Roast the Poblanos
Broil the poblanos until charred and softened, then peel and finely chop.
Prepare the Cream & Cheese Mixture
Combine the cream with garlic, thyme, salt, pepper, chopped poblanos, and two-thirds of the cheese. Taste and adjust seasoning—the mixture should be well seasoned before assembling.
Slice & Coat the Potatoes
Thinly slice the potatoes and toss them directly into the cream mixture as you go. This prevents browning and ensures every slice is evenly coated.
Assemble the Casserole
Arrange the potatoes snugly in the prepared baking dish, layering and spooning cream mixture between layers. Pour in enough cream to reach halfway (or slightly above) up the sides—without overfilling.
Sprinkle all remaining poblanos and cheese from the mixture over the top, gently press to distribute, dot with butter, and cover tightly with foil.
Bake in a Water Bath
Place the covered casserole in a water bath and bake for 50 minutes. Remove the foil and continue baking for about 30 minutes, until the top is lightly golden and the potatoes are almost tender.
Sprinkle the remaining one-third of the cheese evenly over the top and return the casserole to the oven. Bake for about 20 minutes, until the gratin is golden, bubbly, crisp, and the potatoes are fully fork-tender.
Rest and Serve
Let the casserole rest so it sets beautifully. Garnish with parsley and enjoy.
Recipe Video Tutorial
Watch my easy video tutorial for step-by-step visuals on making Au Gratin Potatoes with Poblanos.
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Why You’ll Love This Potato Casserole
- Simple prep, mostly oven time
- Creamy, buttery, and deeply comforting, with rich flavor in every bite
- Aromatic and elegant, yet surprisingly easy to make
- No peeling required — keep the potato skins on for extra fiber and texture
- A cozy, celebratory dish that always earns compliments
Why Use a Water Bath?
After seeing so many questions about cream curdling, I chose to bake this casserole in a water bath (bain-marie) so it cooks gently and evenly. Because it’s rich in cream and cheese, the controlled heat helps protect the sauce from curdling.
Why the Sauce May Separate Slightly
Even with a water bath, a slight separation can happen, especially toward the end of baking. This doesn’t mean the sauce curdled.
- Here’s what’s going on:
As the casserole finishes baking, butterfat and cheese oils naturally rise to the surface. The potatoes have absorbed most of the cream, leaving visible fat on top. This is normal in rich gratins and casseroles.
- The good news?
Resting fixes it. As the casserole sits, the fat redistributes back into the potatoes, the sauce settles, and the texture becomes creamy rather than loose.
Serving Suggestions
These potatoes pair beautifully with chicken dishes like Pollo Loco, jalapeño chicken, baked chicken thighs, or chicken in salsa verde.
For beef, barbacoa, bistec ranchero, or carne asada pair beautifully.
For drinks, serve something refreshing like horchata or cucumber agua fresca, or lean into comfort with atole de café or atole de elote for a warm, cozy finish.
Storage & Reheating Instructions
Refrigerator:
Let the casserole cool completely, then cover tightly or transfer to an airtight container. Refrigerate for up to 4 days.
Freezer:
Wrap the cooled casserole tightly or store it in a freezer-safe container. Freeze for up to 2 months. Thaw in the refrigerator before reheating.
Reheating:
Reheat covered in a 350°F oven until heated through, about 20–30 minutes. You can also reheat gently in the microwave, if preferred.
Frequently Asked Questions
Can I substitute Oaxaca cheese?
Yes. If you can’t find Oaxaca cheese, low-moisture mozzarella is the best substitute.
Why does the cream mixture need to be well seasoned?
Potatoes absorb flavor as they bake, so the cream mixture needs to be nicely seasoned and pleasantly salty. This ensures every layer tastes rich and balanced once baked—without the dish tasting flat.
Why do the potatoes need to be thinly sliced?
Thin, even slices allow the potatoes to cook evenly and become tender at the same time as the cream thickens. A mandoline works best, but a knife is fine—just take your time make them thin enough.
Au Gratin Potatoes with Poblanos
Ingredients
- 3 lbs gold potatoes
- 2 poblanos, halved, seeded, stemmed
Milk and Cheese Mixture
- 2 cups heavy cream
- 4 oz gouda cheese, freshly grated (not pre-shredded)
- 4 oz queso Oaxaca, freshly grated (not pre-shredded)
- 2 oz parmesan cheese, freshly grated (not pre-shredded)
- 4 garlic cloves, finely minced
- 1 tbsp fresh thyme, finely chopped
- To taste kosher salt, (1.5 tsp)
- To taste black pepper, freshly ground
- 2 tbsp unsalted butter, diced
Additional
- Parsley, finely chopped
- Avocado oil, as needed
Instructions
Roast the Poblanos
- Preheat the oven to broil (high). Line a quarter– or half-sheet pan with aluminum foil. Arrange the poblanos skin-side up and lightly drizzle with oil.
- Broil on the lower third rack from the top until the skins are charred and the peppers are softened, about 10–15 minutes.
- Remove from the oven and let cool slightly. Peel off the skins, then cut the poblanos into small squares and run your knife through them again to finely chop. Set aside.
Make the Cream & Cheese Mixture
- In a medium bowl, combine the three cheeses and mix until evenly distributed.
- In a large bowl, combine the garlic, thyme, and cream. Add two-thirds of the cheese mixture, the salt (about 1½ teaspoons kosher salt), freshly ground black pepper, and the chopped poblanos.
- Stir until well combined, then taste and adjust the seasoning—the mixture should be well seasoned and pleasantly salty.
- Preheat the oven to 375°F.
Prepare the Potatoes
- Slice the potatoes thinly, about ⅛-inch thick, using a sharp knife or mandoline for even slices. As you slice, add the potatoes directly to the cream mixture to prevent browning.
- Once all the potatoes are sliced, gently toss them with your hands to ensure they are fully coated, being careful not to break them.
Assemble the Casserole
- Lightly grease an 11½ × 8¼-inch oval casserole dish (comfortably fits 2 quarts) with nonstick spray.
- Lift the potatoes from the cream mixture in small batches, stack them, and arrange them upright at a slight angle in the dish.
- Continue until the bottom is fully covered, forming a tight spiral pattern. Spoon a small amount of the cream mixture—along with some of the cheese and poblanos—over the potatoes, just enough to lightly cover them.
- Repeat the stacking and layering process to create a second layer.
- Pour the remaining cream mixture evenly over the potatoes. The liquid should reach about halfway or slightly above halfway up the sides of the dish—you don’t want it completely full. It’s fine if you don’t use all of the cream.
- Make sure all of the poblanos and cheese from the cream mixture are evenly distributed throughout the casserole. Gently press down to help the cream settle between the layers, then dot the surface with butter.
- Cover the casserole tightly with aluminum foil—lightly spraying the foil with nonstick spray helps prevent sticking as the cheese melts.
Water Bath Bake
- Place the casserole dish inside a larger roasting pan or baking dish. Carefully pour water into the outer pan until it reaches about halfway up the sides of the casserole, creating a water bath.
- Carefully transfer to the center rack of the oven and bake for 50 minutes.
- Remove the foil and continue baking uncovered for 30–35 minutes, or until the top begins to brown and turn lightly golden. The potatoes should be mostly tender, offering just slight resistance when pierced with a fork.
- Carefully remove the casserole from the oven, keeping it in the water bath. Evenly sprinkle the remaining one-third of the reserved cheese over the top, then return it to the oven.
- Bake for an additional 20–25 minutes, until the top is golden, bubbly, and crisp, and the potatoes are fully fork-tender.
- Remove from the oven, then carefully lift the casserole dish out of the water bath and transfer it to a wire rack.
Rest and Serve
- Let rest for 15–20 minutes before serving to allow the casserole to set. Garnish with fresh parsley and serve.
Equipment
- 11½ × 8¼-inch oval casserole dish
- Aluminum Foil
Notes
Nutrition
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