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The onions start out sharp and crisp in the skillet, then slowly soften until they turn deep gold and sweet. I used to rush this part, thinking the potatoes would make up for onions that were only lightly cooked. They don’t. In caramelized onion mashed potatoes, the onion flavor needs time to mellow so it blends into the buttery mash instead of competing with it.

Yukon Gold potatoes give this version a naturally creamy texture, and warming the butter with the cream keeps the dairy from cooling the potatoes when it goes in. The onions cook separately, which lets you watch their color and keep them from browning too fast while the potatoes simmer.

Once the onions are folded through, every scoop has soft, golden strands tucked into the potatoes. The finished mash is rich without losing the gentle sweetness that makes the onions worth the extra time.

Why the Onions Need More Time Than Your Instinct Says

Thinly sliced onions can look ready long before they have the soft, mellow character this mash needs. A little color at the edges isn’t the same as onions that have cooked down all the way. Give them time to soften throughout and turn deep golden; that’s when their sharper bite gives way to a sweeter, rounded flavor.

Medium-low heat keeps the transformation gradual. If the onions darken quickly while the slices still feel firm, the skillet is running too hot. Lower the heat rather than trying to hurry them along. Stirring often helps the slices cook evenly and keeps the bottom layer from catching while the rest of the pan softens.

That long cook is also what makes the onion flavor work with the potatoes instead of sitting on top of them. The mash is mild and creamy, so harsh, browned edges stand out. Soft, evenly cooked onions fold in more naturally and leave sweet strands throughout the bowl.

Why Yukon Golds Hold This Onion-Studded Mash Together

• Yukon Gold potatoes — Their naturally buttery, creamy texture suits a mash that needs to carry soft onion strands without turning watery. Choose firm potatoes without soft spots. Peeling them gives the finished mash a more even texture; keeping the chunks close in size helps them cook at the same pace.
• Yellow onions — These soften into a mellow sweetness that fits the potatoes. Fresh, firm onions are all you need here; there’s no benefit to using a specialty variety. Thin, even slices matter more than perfect knife work because they cook down at a similar rate.
• Unsalted butter and heavy cream — Butter brings richness, while heavy cream gives the mash its full, smooth feel. Unsalted butter lets the kosher salt stay in balance instead of adding an unknown level of saltiness. The cream doesn’t need to be an expensive brand; use one that’s fresh and full-fat for the texture this recipe is built around.
• Olive oil — It gives the onions a little fat to cook in without taking over their flavor. A basic olive oil works well here, so save your most delicate finishing oil for another use.

The Slow Onion Cook and the Potato Timing

Let the Onions Turn Soft and Deep Golden

Heat the olive oil in a 12-inch skillet over medium-low heat, then add the thinly sliced onions. Stir often as they cook for 35 to 45 minutes, watching for the slices to become very soft and deep golden rather than sharply browned. If they begin to brown too quickly, lower the heat. Transfer the finished onions to a bowl and set them aside.

Simmer the Potatoes Until Fork-Tender

Put the peeled potato chunks in a 5-quart pot and cover them with cold water by 1 inch. Stir in 1 tablespoon of the kosher salt, bring the water to a boil over high heat, then reduce it to a gentle simmer. Cook for 15 to 20 minutes, until a fork slides into the potatoes easily. A vigorous boil can knock the chunks around, so keep the simmer gentle once the pot comes to a boil.

Warm the Butter and Cream Gently

While the potatoes cook, put the butter pieces and heavy cream in a small saucepan over low heat. Warm them for 3 to 4 minutes, until the butter melts and the cream is steaming. Don’t let the mixture boil. Keep the heat low enough that the cream warms steadily without bubbling at the edges.

Dry, Mash, and Fold in the Onions

Drain the potatoes well, then return them to the pot over low heat for 1 minute, stirring gently so excess moisture can evaporate. Remove the pot from the heat and add the warm butter and cream, the remaining 1 teaspoon of kosher salt, and the black pepper. Mash to your preferred texture, then fold in the caramelized onions and serve hot. Folding at the end keeps the onion strands visible instead of breaking them down through the mash.

Two Ways to Change the Onion Finish Without Changing the Ingredients

Questions I Get Asked About Caramelized Onion Mashed Potatoes

Caramelized Onion Mashed Potatoes

Caramelized onion mashed potatoes combine buttery Yukon Golds with onions cooked low and slow until very soft and deep golden. Warm cream and butter make the potatoes rich and smooth, while black pepper adds a savory finish.

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Prep Time 15 minutes mins

Cook Time 59 minutes mins

Total Time 1 hour hr 14 minutes mins

Servings: 6 servings

Course: Side Dish

Cuisine: American

Calories: 440

Ingredients Equipment Method Notes

Ingredients

  

For the caramelized onions

• 1 tbsp olive oil
• 2 yellow onions large, thinly sliced

For the mashed potatoes

• 3 lb Yukon Gold potatoes peeled and cut into 1 1/2-inch chunks
• 1 tbsp kosher salt for the cooking water
• 1 tsp kosher salt for the potatoes
• 6 tbsp unsalted butter cut into pieces
• 0.75 cup heavy cream
• 0.5 tsp black pepper

Equipment

• 1 12-inch skillet

Method

 

Caramelize the onions

1. Heat the olive oil in a 12-inch skillet over medium-low heat, add the onions, and cook for 35 to 45 minutes, stirring often, until very soft and deep golden; lower the heat if they begin to brown too quickly.
2. Transfer the onions to a bowl and set aside.

Make the mashed potatoes

1. Put the potatoes in a 5-quart pot, cover with cold water by 1 inch, and stir in 1 tablespoon of the salt. Bring to a boil over high heat, then reduce to a gentle simmer and cook for 15 to 20 minutes, until the potatoes are fork-tender.
2. While the potatoes cook, warm the butter and cream in a small saucepan over low heat for 3 to 4 minutes, until the butter melts and the cream is steaming; do not let it boil.
3. Drain the potatoes well and return them to the pot over low heat for 1 minute, stirring gently to let excess moisture evaporate.
4. Remove the pot from the heat, add the warm butter and cream, the remaining 1 teaspoon salt, and the black pepper, then mash to your preferred texture.
5. Fold in the caramelized onions and serve hot.

Notes

Cook the onions slowly and lower the heat if they begin to brown too quickly, so they turn very soft and deep golden. Refrigerate leftovers for 3 to 4 days; freezing is possible, though the texture may change. For a dairy-free swap, use plant-based butter and unsweetened plant-based cream.