Mashed potatoes have always been a crowd-pleaser, but these Caramelized Onion Mashed Potatoes are elevated to a whole new level of deliciousness. They are the perfect balance between simplicity and indulgence.
The velvety, buttery, creamy mashed potatoes are infused with the rich, sweet-savory goodness of caramelized onions and a sprinkle of earthy thyme. Giving you a side dish with the warmth and comfort that good food brings.
So whether you're gearing up for a festive holiday feast, a hearty Sunday roast, or a simple midweek meal with chicken or steak, this recipe is your ticket to comfort-food heaven.
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These notes are here to help make this Caramelized Onion Mashed Potato recipe a success; they cover some but not all ingredients; for a complete ingredient list, check out the recipe card below.
Potatoes: You want to pick a floury potato for this recipe. Russet, Maris Piper, or Sebago are perfect for this recipe.
Onions: Any onion you have will work in this recipe. I use regular brown onions, but you can use white, yellow, or brown onions. You could even use a red onion.
Butter: I use good quality salted butter for this. Kerrygold is widely available and has a great flavor. If you use unsalted butter, be ready to add extra seasonings to the mashed potatoes.
Thyme: The recipe uses fresh thyme leaves, but you can substitute dried.
Cream: The recipe calls for heavy/thickened/double cream. You can substitute half and half, single cream, or milk, but the resulting potato will be less creamy.
Dijon mustard: This balances the sweetness of the caramelized onions, but you can leave it out.
We've tested this recipe at least 3 times to ensure it works well for you, have a look at our tips for getting the best dish you can!
- Cook the onions over medium-low heat so they become meltingly tender and color slowly. This releases the natural sweetness in the onion.
- Add plenty of salt to the cooking water.
- Cook the potatoes until they are very soft. They should be soft enough that if you push a knife into them, they fall in half.
- After draining the potatoes, leave them in the sieve or colander for several minutes to steam dry.
- Use a potato masher or a ricer. Anything electric will give you a gluey gummy mashed potato.
- Mash the potatoes while they are still hot to get the fluffiest texture.
- Mix the butter and cream into the mashed potatoes with a wooden spoon to get a smooth creamy mash.
Why You'll Love These Caramelized Onion Mashed Potatoes
These are all just suggestions and things that have worked in our test kitchen, but it is your dinner, so adapt it to suit your family. That is the beauty of cooking; we can all create our own delicious meals.
- Garlic: Add some finely chopped garlic to the onions for the last 5 minutes of cooking.
- Cheese: Add shredded cheddar or mozzarella to your mashed potatoes for a cheesy onion mash.
- Herbs: Change the thyme for rosemary, sage, or oregano.
- Bacon: Add crispy bacon bits to your finished mashed potatoes.
- Veg: Add leeks in with the onions, or stir through some defrosted spinach or kale for nutritious addition.
- Mustard: You can swap the Dijon mustard for spicy English mustard or wholegrain mustard or use prepared horseradish instead.
Serving Suggestions for Caramelized Onion Mashed Potatoes
For other potatoes recipes try:
- Crispy Pan Fried Potatoes
- Crispy Garlic Butter Potatoes
- Slow Roasted Greek Lemon Potatoes
- French Style Mashed Potato
If you make these Caramelized Onion Mashed Potatoes, please come back and comment. You can also tag me on social media.
Any questions about the recipe? Use the comments section below.
Get the Recipe
Caramelized Onion Mashed Potatoes
For the onions
- 2 tablespoon butter
- 1 tablespoon oil
- 3 onions
- ¼ teaspoon salt
- 1 tablespoon thyme leaves
For the potatoes
- 3 lb potatoes , peeled and cut into 2.5cm/1" chunks
- 1 tablespoon salt
- 4 tablespoon butter
- ½ cup heavy cream
- 1 tablespoon Dijon mustard
- ¼ teaspoon pepper
Start with the onions
- Melt the butter and oil together in a large skillet or frying pan.2 tablespoon butter1 tablespoon oil
- Once melted, add the onions, salt, and thyme leaves. Stir to coat the onions in the butter, then cook over medium-low heat for 20-25 minutes, stirring occasionally.3 onions¼ teaspoon salt1 tablespoon thyme leaves
While the onions are cooking, start the potatoes.
- Bring a pan of water to a boil, then add the salt and potatoes.1 tablespoon salt3 lb potatoes
- Cook for around 12-15 minutes until the potatoes are very soft. You should be able to push a fork through them easily.
- Drain the potatoes and let them steam in the sieve or colander for 2 minutes before returning them to the pan.
- Use a potato masher or a potato ricer to mash the potatoes.
- Add the butter, cream, dijon mustard, and pepper, then stir well with a wooden spoon.4 tablespoon butter½ cup heavy cream1 tablespoon Dijon mustard¼ teaspoon pepper
- Stir in the onions, then taste and add more salt if needed.
- Serve scattered with extra thyme leaves.
Nutrition is per serving