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How to Make Cheesy Mashed Potatoes with Caramelized Onion

Cheesy mashed potatoes are fully loaded with melted Gruyere cheese and the sweetness of beautifully golden caramelized onions. They are as easy to make as they are impressive and will definitely become the star of any meal!

These cheesy mashed potatoes with Gruyere and caramelized onions are next-level good. They’re definitely not your ordinary mashed potatoes and are a surefire way to impress your guests when served on the side of grilled meat, fish, or anywhere you’d find a dollop of mashed potatoes.

However, even a juicy steak and a grilled lobster tail won’t outshine the incredible depth of flavor in these potatoes! 

How to Make Cheesy Mashed Potatoes with Caramelized Onion

As much as these are a jazzed-up version of regular mashed potatoes, they’re just as simple and comforting as a part of any simple weeknight meal because of how easy they are to do.

It’s just a matter of cooking down the onions and boiling potatoes and that, my friends, is really it!

Caramelizing onions isn’t difficult at all, and once you know how to make them, you’ll be finding any excuse to use them. Enjoy them on top of caramelized onion hamburgers, as a topping on bacon spinach and artichoke pizza, on nachos, and of course in your French onion soup!

ingredients needed to make best mashed potatoes

If I were you, I’d make more than you need this time around and save the rest for meals throughout the week!

Ingredients Needed For the mashed potatoes

  • Golden potatoes – Cut into cubes to boil. Golden potatoes have thin, delicate skin so it’s up to you whether you want to peel them or not.
  • Sea salt – Will be used to season the potatoes but also to salt the water.
  • Whole milk – Adding warm milk to the potatoes gives them a creamy consistency and helps give them a bit of liquid needed for mashing.
  • Butter – Melted butter drizzled into mashed potatoes adds a delicious buttery flavor you don’t want to skip.
  • Black pepper – A little seasoning goes a long way. These potatoes will have a ton of flavor from all of the added ingredients.
  • Gruyere cheese – A rich, creamy, Swiss cheese that melts so beautifully. Freshly grated Gruyere adds a sharp contrast to the creamy potatoes. So good!
  • Parsley – Just a bit for garnish!

For the caramelized onions

  • Onion – Depending on what you use it for some recipes will require you to caramelize slices or rings of onions. In this case, you want to dice the onions and then cook them.
  • Butter – There’s just something about cooking onions in butter that makes your mouth water isn’t there? You can also use oil if you prefer.
  • Sugar – Just a bit of sugar to help get the process going. Cooking the onions down in butter with a bit of sugar to help get them golden brown and yummy.
  • Salt & pepper – A sprinkle, to taste.

how to make caramelized onions


How to Make Cheesy Mashed Potatoes

Step 1: First thing’s first, you need to caramelize the onions. Add butter, onion, sugar, and salt to a skillet (I am using a cast-iron skillet) and sauté over medium heat, stirring occasionally.

caramelized onions

Step 3: Cook for 20-30 minutes, or until the onions are caramelized. Stir a few times along the way to ensure even cooking and avoid burnt bits. Add more butter or oil if needed. Set caramelized onions aside.

boiling potatoes for mashed potatoesStep 4: Add potatoes to a large pot and add just enough water to cover the potatoes. Add salt and bring the water to a boil over medium-high heat. Cook until potatoes are fork-tender. This should be about 20 minutes (8 if you’re using an Instant Pot!).

making mashed potatoesmaking potatoes with milk and butter

Step 5: Drain the potatoes and return them back to the pot. Using a potato masher, begin mashing. Add milk, butter, salt, and pepper, then mix using a hand mixer.potatoes mixed with milk and butter using hand mixer

cheesy mashed potatoes

Step 6: Grab the caramelized onions and toss about 1 cup of them into the potatoes along with 1 cup of cheese. Stir to combine.

cheesy mashed potatoes with caramelized onions

Step 7: Serve warm garnished with parsley and a sprinkle of black pepper, if desired.

Top Tips

  • Gruyere cheese isn’t cheap, so I try to pick it up on sale or save this recipe for the holidays.
  • Don’t skip salting the water for the potatoes. Saltwater boils faster but it also helps to enhance flavor and avoid potato starch clumping together.
  • Do not over mix the potatoes. Overdoing it is one way to ensure goopy and gluey potatoes!
  • Use either yellow or white onions or a combination of both.
  • Sprinkle cooked crispy bacon over the top for extra garnish.


Mashed Potatoes with Caramelized Onion

Ways to Serve Creamy Mashed Potatoes with Caramelized Onion

These easy mashed potatoes have so much flavor and texture that make them pretty much perfect on the side of all your favorites. Replace your everyday mashed potatoes with this jazzed-up version to complete any meal!

Serve on the side of a bacon wrapped filet mignon with shrimp or a ribeye steak cooked on the stove for fancier occasions or on the side of Instant Pot roast beef and gravy for Sunday dinner.

Enjoy cool and creamy mashed potatoes alongside spicy grilled shrimp or fried chicken cutlets.

What Cheese Can I Substitute for Gruyere?

When I crave it for a casual weeknight dinner and don’t have any Gruyere on hand, I’ll substitute for Emmental or Jarlsberg. They have much the same properties in terms of taste, how well they melt, how creamy and velvety they are.

Do I Need to Add the Sugar to the Caramelized Onions?

Technically you don’t. It’s not much at all, it’s just a little extra sweetness that I enjoy the flavor of, but by all means, leave it out. Onions will sweeten and caramelize naturally without it.

How to Store Cheesy Mashed Potatoes?

Keep leftover mashed potatoes in the fridge for up to 3 days in an airtight container. If you’ve made more than enough caramelized onions, they’ll keep for up to 5 days in the fridge. Like I said, use them up in a variety of ways, like cooking for breakfast with eggs and chicken sausages, making mashed macaroni (my kid’s favorite), or making homemade perogies

mashed potatoes with caramelized onions and cheese garnished with chopped parsley and melted butter

How to Make Mashed Potatoes with Caramelized Onion and Cheese

Love Keil
How to make Cheesy mashed potatoes with melted Gruyere cheese & delicious caramelized onions. This is the best mashed potatoes recipe ever.
5 from 1 vote
Prep Time 10 minutes
Cook Time 40 minutes
Course Side Dish
Cuisine American
Servings 6 servings
Calories 494 kcal


To Make Mashed Potatoes

  • 4 lb golden potatoes cut into 2 inch cubes
  • 1 teaspoon sea salt plus more for boiling water
  • 1 1/4 cup whole milk warm
  • 5 tablespoons butter melted
  • 1/2 teaspoon black pepper or to taste
  • 1 cup Gruyere cheese grated, more if desired
  • parsley finely chopped for garnish

To Make Caramelized Onion

  • 2 large onion diced
  • 2 tablespoons butter or use olive oil
  • 1/2 teaspoon sugar
  • salt and pepper to taste


How to Make Caramelized Onion

  • Start making caramelized onion first. To make caramelized onion add butter, onion, salt and sugar to the skillet and sauce over medium heat, stirring occasionally.
  • Cook for 20-30 minutes, or until onions are caramelized, stirring a few times. Be careful not to burn it (adding more butter or oil if needed).

 How to Make Mashed Potatoes

  • While onions are cooking add cubed potatoes into a pot and add water to cover, 2 teaspoons of salt, and bring it to a boil over medium-high heat. Cook for 20 minutes or until potatoes are tender when pierced with a knife. Drain.
  • Mash potatoes with a potato masher. Next, add milk, butter, salt and pepper, mix using a hand mixer.
  • Next, stir in caramelized onions about 1 cup and 1 cup of cheese, stir until everything is combined. Garnish with freshly chopped parsley and sprinkle black pepper over the top.


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Calories: 494kcalCarbohydrates: 60gProtein: 15gFat: 22gSaturated Fat: 14gPolyunsaturated Fat: 1gMonounsaturated Fat: 6gTrans Fat: 1gCholesterol: 64mgSodium: 620mgPotassium: 1437mgFiber: 8gSugar: 7gVitamin A: 707IUVitamin C: 63mgCalcium: 333mgIron: 3mg
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