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Caramelized Onion Mashed Potatoes

Caramelized Onion Mashed Potatoes with silky Yukon gold mash and ribbons of deep golden-brown onions. Cook the onions low and slow, then fold them into warm, creamy potatoes for a rich side dish.
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Prep Time 15 minutes
Cook Time 40 minutes
Total Time 55 minutes
Servings: 8 servings
Course: Side Dish
Cuisine: American
Calories: 320
Ingredients Equipment Method Notes

Ingredients
  

butter
  • 3 tbsp unsalted butter plus 4 tablespoons for mashing
  • 4 tbsp unsalted butter for mashing
onions
  • 2 large yellow onions thinly sliced
  • 0.5 tsp salt for onions
  • 1 tsp fresh thyme leaves
potatoes
  • 3 lb Yukon gold potatoes peeled and cubed
  • 1 tbsp salt for the water
dairy
  • 0.75 cup heavy cream warmed
  • 0.5 cup sour cream
seasonings
  • 1 tsp salt
  • 0.25 tsp black pepper

Equipment

  • 1 cast iron skillet

Method
 

Caramelize the onions
  1. Melt 3 tablespoons butter over medium-low heat, then add the thinly sliced onions and salt for onions. Cook, stirring often, for 30-35 minutes until deep golden brown.
  2. Stir in fresh thyme leaves and cook for 30 seconds, just until fragrant, keeping the heat at medium-low.
Boil and mash the potatoes
  1. Boil the Yukon gold potatoes in salted water (with salt for the water) for 15-18 minutes, until tender. Drain well.
  2. Mash the drained potatoes with the remaining butter, warm heavy cream, and sour cream until smooth and creamy.
Combine and serve
  1. Fold in most of the caramelized onions, then season with salt and black pepper. Mix until evenly distributed.
  2. Top the mashed potatoes with the remaining caramelized onions and serve.

Notes

For extra creamy texture, warm the heavy cream before mashing so the potatoes stay smooth. Store leftovers in an airtight container in the fridge up to 3 days; reheat gently on the stovetop with a splash of cream or milk to loosen. Freezing is not recommended because the onions and dairy can break. If you need a dairy-light option, use half-and-half in place of heavy cream and sour cream.