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.
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
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.
More details are shared above in the article.
Nutrition
Serving: 1SERVINGCalories: 496kcalCarbohydrates: 35gProtein: 15gFat: 34gSaturated Fat: 22gPolyunsaturated Fat: 1gMonounsaturated Fat: 8gTrans Fat: 0.1gCholesterol: 101mgSodium: 384mgPotassium: 861mgFiber: 4gSugar: 4gVitamin A: 1255IUVitamin C: 60mgCalcium: 261mgIron: 2mg
Nutrition information is automatically calculated and intended as an approximation only.