Cast Iron Skillet Potatoes with Caramelized Onions

Name: Cast Iron Skillet Potatoes with Caramelized Onions
Prep time: 15 min
Cook time: 50 min
Total time: 1 h 5 min
Yield: 4 servings
Cuisine: American
Ingredients: 1½ lb (680 g) Yukon Gold potatoes, unpeeled, cut into ¾-inch (2 cm) cubes; 1 lb (450 g) yellow onions, halved lengthwise and sliced into ¼-inch (6 mm) half-moons; 4 tablespoons (57 g) unsalted butter, divided (3 tablespoons for onions, 1 tablespoon for potatoes); 2 tablespoons (30 ml) extra-virgin olive oil; 4 sprigs (5 g) fresh thyme sprigs, leaves stripped from stems (about 1 tablespoon total), or 1 teaspoon dried thyme; to taste kosher salt; to taste freshly ground black pepper; 2 cloves (6 g) garlic cloves, minced (optional)

From the MyKitchenBank Kitchen

Golden crispy potatoes tossed with sweet, deeply caramelized onions and fresh thyme, all cooked in a cast iron skillet until the bottoms are nutty and browned. The potatoes turn golden while the onions slowly transform into silky, jammy sweetness. A simple but elegant side that pairs beautifully with roasted meats or can stand alone.

Prep: 15 min
Cook: 50 min
Total: 1 hr 5 min
Makes: 4 servings (about 1¼ cups per person)

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Steps

Before you start

Preheat your 10 or 12-inch cast iron skillet over medium-high heat for 2 minutes
Have all ingredients prepped and within reach—the caramelized onions need frequent attention
Use waxy potatoes like Yukon Gold; they hold their shape better than russets

1
Start the caramelized onions
- Reduce heat to medium and add 3 tablespoons (43 g) butter to the hot skillet.
- Once foaming, add the sliced onions and ¼ teaspoon salt.
- Stir to coat, then let them sit undisturbed for 3–4 minutes to begin softening and browning on the bottom.
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Ready when: Onions are light golden brown on the bottom
Tip: Don't stir too early or often—you want the bottoms to caramelize and develop deep color
2
Continue caramelizing
- Stir the onions well, scraping up any browned bits stuck to the pan.
- Reduce heat to medium-low and cook, stirring every 2–3 minutes, for 25–30 minutes total.
- They will gradually turn from pale gold to deep amber and become soft and jammy.
- Add minced garlic (if using) in the last 5 minutes.
- The onions should smell sweet and nutty, with no raw onion smell remaining.
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Ready when: Onions are dark amber, very soft, and smell sweet and nutty
Tip: Low, slow heat is the key to sweet caramelization; high heat will burn them before they soften
3
Move onions aside, cook potatoes
- Push the caramelized onions to one side of the skillet, leaving a clear space for the potatoes.
- Add the 1 tablespoon (14 g) remaining butter and 2 tablespoons (30 ml) olive oil to the empty side.
- Increase heat to medium-high.
- Once the butter is foaming, add the cubed potatoes in a single layer (work in two batches if needed to avoid crowding).
- Season with ½ teaspoon salt and several cracks of pepper.
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Tip: Crowding the pan lowers the temperature and causes steaming instead of browning—use a large skillet or batch
4
Brown potatoes without stirring
- Let the potatoes sit undisturbed for 5–6 minutes.
- They will develop a golden-brown crust on the bottom.
- Resist the urge to stir—this is how they get crispy.
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Ready when: Potatoes are golden brown on the bottom (peek with a spatula if unsure)
Tip: Use a cast iron skillet—its heat retention ensures even, crispy browning
5
Turn and continue cooking
- Stir and toss the potatoes, breaking up any that stuck together.
- Cook for another 5–6 minutes without stirring, then stir again and cook until all sides are golden and crispy and the potatoes are tender when pierced with a fork.
- Total potato cooking time is 15–18 minutes.
- If potatoes are tender outside but still firm inside, cover the skillet loosely and reduce heat to medium for 2–3 minutes to finish cooking through.
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Ready when: All sides of potato cubes are golden brown and flesh is very tender when pierced
Tip: Stir in two stages (after 5–6 minutes, then again) to maximize crispy surface area on all sides
6
Combine and season
- Add the fresh thyme leaves (or dried thyme if using) to the potatoes and gently fold everything together, mixing the crispy potatoes with the caramelized onions.
- Taste and adjust seasoning with additional salt and pepper as needed.
- The potatoes should be salty and well-seasoned, with the sweetness of the onions balancing the savory potato flavor.
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Ready when: Potatoes and onions are evenly combined and flavors taste balanced
Tip: Fold gently to keep the crispy potato cubes intact; rough stirring will break them down
7
Serve immediately
- Transfer to a serving bowl or serve directly from the skillet.
- The potatoes are best eaten hot, while the potatoes are still crispy and the skillet releases residual warmth.
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Tip: If serving in the cast iron skillet, warn guests it is very hot to the touch

Good to know

Tips

Use a cast iron skillet—it distributes heat evenly and creates the best crust on the potatoes. A regular stainless steel or non-stick pan will still work but won't brown as evenly.
Don't skip the undisturbed cooking periods for both onions and potatoes. The time without stirring is what creates the caramelization and crispy edges that make this dish special.
For extra richness, stir a spoonful of aged balsamic vinegar or whole grain mustard into the caramelized onions just before combining with the potatoes.
If your potatoes are done well before your onions are fully caramelized, keep the potatoes warm by covering the skillet loosely or transferring them to a 200°F (93°C) oven.

Make ahead

The caramelized onions can be made up to 2 days ahead and stored in an airtight container in the refrigerator. Reheat gently in a skillet over medium heat before combining with the potatoes. The potatoes must be cooked and served fresh for maximum crispiness.

Storage & reheating

Store leftovers in an airtight container in the refrigerator for up to 3 days. The potatoes will lose crispiness over time. Reheat in a cast iron skillet over medium heat, stirring occasionally, until warmed through and edges re-crisp (about 5 minutes). Do not freeze, as the texture of the potatoes will suffer.

Substitutions

Yukon Gold potatoes, unpeeled → Red potatoes or fingerling potatoes. Fingerlings are especially good for this recipe; cut them in half or thirds instead of cubes. Red potatoes are slightly firmer and take a few minutes longer to cook.
yellow onions → Sweet onions (Vidalia or Walla Walla) or red onions. Sweet onions caramelize faster and need only 20–25 minutes; red onions will turn a beautiful deep burgundy and take the full 30 minutes.
fresh thyme sprigs → Rosemary or sage. Use 1 teaspoon dried rosemary or ½ teaspoon dried sage for a different herb flavor; both pair beautifully with caramelized onions and potatoes.
unsalted butter → Ghee or duck fat. Ghee adds a toasted, nutty flavor; duck fat creates an ultra-crispy exterior on the potatoes and richer taste overall.