French Onion Mashed Potatoes
These French Onion Mashed Potatoes are the ultimate mashup of two beloved comfort food dishes! These potatoes are super buttery, creamy, and cheesy with nutty Gruyere cheese and decadent caramelized onions. This elegant side dish is truly a star, but also allows main dishes to shine!
Servings: 14 servings
Calories: 563kcal
Ingredients
Caramelized onions
- ¼ cup unsalted butter 1 stick
- 5 medium sweet onions thinly sliced
- ½ teaspoon kosher salt
- 6 cloves garlic minced
- 1 tablespoon balsamic vinegar
- 1 tablespoon Worcestershire sauce
- 1 tablespoon sugar
Potatoes
- 6 pounds potatoes cut into roughly even sized chunks (not too small or they will soak up too much water)
- ¾ cup unsalted butter 3 sticks
- 3 cups cream
- 6 ounces gruyere cheese
- 1 ½ teaspoons black pepper to taste
- 4-5 teaspoons kosher salt
Instructions
Caramelized onions
- Heat the butter in a skillet over medium-low heat. Add the onions with a big pinch of salt. Cook for 10 minutes, stirring often, so the onions begin to cook down.¼ cup unsalted butter, 5 medium sweet onions, ½ teaspoon kosher salt
- Add in fresh thyme sprigs, garlic, sugar, Worcestershire sauce, and balsamic, and stir for about 1 minute, then reduce the heat to low.6 cloves garlic, 1 tablespoon balsamic vinegar, 1 tablespoon Worcestershire sauce, 1 tablespoon sugar
- Continue to cook, stirring occasionally, until the onions are golden and caramelized, about 45 to 60 more minutes. You can't speed this process up!
Potatoes
- Meanwhile, llace the potatoes in a large pot of cold water over medium heat. Season the water with roughly 1 tablespoon of kosher salt per pound of potatoes. Bring the potatoes to a boil, then boil until they are fork tender, about 13 to 15 minutes. (If your potato chunks are smaller, check after 10 minutes.)6 pounds potatoes
- While the potatoes are boiling, heat the butter and cream in a saucepan over medium-low heat until the mixture is warmed through.¾ cup unsalted butter, 3 cups cream
- Mash the potatoes by hand to avoid overmixing, stir in the cream and butter mixture, don't over mash the potatoes, mixing in the cheese simultaneously while the potatoes are warm to ensure the cheese melts.6 ounces gruyere cheese
- Stir in about half of the caramelized onions, reserving more for serving. Taste, then add salt and pepper.1 ½ teaspoons black pepper, 4-5 teaspoons kosher salt
- Serve with more butter, salt, pepper, and fresh thyme. Enjoy!
Notes
Caramelized onion tips
- Start with the right onions. Sweet onions (Vidalia, Walla Walla, or Maui) have more natural sugar and caramelize beautifully with less bitterness. Yellow onions work well, too. Avoid red onions—they can be too sharp or become an unappealing red-grey color.
- Slice uniformly. Slice onions thinly and consistently (about ¼ inch thick) so they cook evenly. Uneven slices mean some pieces burn while others don't cook properly.
- Don't rush the process. True caramelization takes 45-60 minutes. If a recipe claims "caramelized onions in 10 minutes," you can't trust it; there's no such thing as a "quick" caramelized onion! Low and slow is the only way to develop deep, sweet, complex flavor, so be patient.
- Deglaze if needed. If the onions start to stick or develop brown bits on the bottom of the pan, add a tablespoon of water, wine, or broth, and scrape up those browned bits. This is just flavor! However, you don't want anything to burn, so keep a close eye on them.
Mashed potato tips
- Salt the cooking water generously. This is your only chance to season the potatoes from the inside. You want about 1 tablespoon of kosher salt per pound of potatoes, don't be shy!
- Start with cold water. Place potatoes in cold water, then bring to a boil. This ensures even cooking. If you add potatoes to already-boiling water, the outside cooks faster than the inside.
- Don't overcook the potatoes. Boil just until fork-tender (a fork slides in easily, but the potato doesn't fall apart). Overcooked potatoes absorb too much water and become mushy. Check after 10-12 minutes if your chunks are on the smaller side.
- Drain the potatoes and dry again in the Dutch oven. After draining, return the potatoes to the hot pot over low heat for a few minutes. This allows excess moisture to evaporate, resulting in fluffier, less watery potatoes.
- Heat your cream and butter. Cold dairy will cool down your potatoes and make them harder to mash smoothly.
- Mash by hand. Use a potato masher to avoid over-mashing. Don't use a food processor, immersion blender, or electric mixer. This will overwork the starches and create gluey, gummy potatoes.
- Add dairy gradually. Start with about half the cream and butter mixture, mash until combined, then add more as needed. You can always add more liquid, but you can't take it away.
- Fold in cheese while the potatoes are hot. Add the cheese while the potatoes are still hot so it melts smoothly and incorporates evenly. Cold cheese won't melt properly and will leave clumps.
- Taste and adjust. Mashed potatoes need more salt than you think. Taste after mixing in the onions and cheese, then add salt and pepper gradually until they're seasoned just how you like!
Nutrition
Calories: 563kcal | Carbohydrates: 46g | Protein: 10g | Fat: 39g | Saturated Fat: 24g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 10g | Trans Fat: 1g | Cholesterol: 114mg | Sodium: 888mg | Potassium: 1041mg | Fiber: 5g | Sugar: 10g | Vitamin A: 1376IU | Vitamin C: 45mg | Calcium: 214mg | Iron: 2mg