The Ultimate French Onion Mashed Potatoes

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These mashed potatoes are the definition of rich, cozy comfort food. The Boursin adds incredible flavor without any extra effort, the sour cream and butter make them ultra-creamy, and the caramelized onions on top bring a sweet, savory layer that takes them over the top. Finish with melted cheese and you've got a side dish that steals the show every time.

Need a dairy free version? Try my Whole30 Mashed Potatoes instead! Still super creamy and delicious!

Why You'll Love These

• Creamy, flavorful mashed potatoes with no complicated steps
• Boursin adds herbs and richness effortlessly
• Caramelized onion topping makes them restaurant-level
• Perfect for holidays, parties, or any comfort-food dinner

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Ingredients Needed

For the mashed potatoes:

• 5 lbs. potatoes, peeled and cut into chunks
• 1 (5.2 oz.) package Boursin cheese (any flavor works-Garlic & Fine Herbs is classic)
• 1 stick (½ cup) butter
• ½-1 cup sour cream
• ¼-½ cup milk (use only if needed for thinning)
• Salt and pepper to taste

Caramelized Onion Topping

• 3 large onions, thinly sliced
• 2-3 tbsp. butter
• Pinch of salt
• 1-2 tsp. coconut aminos (optional, for depth)

Cheese Topping

• 1-2 cups shredded cheese of choice (see below for options!)

Variations and Substitutions

• For the cheese topping, gruyere is a great option! Trader Joe's also has a caramelized onion cheddar cheese that works perfectly!
• Use olive oil or palm oil in place of the butter to caramelize the onions.
• Try some balsamic glaze or Worcestershire sauce instead of the coconut aminos.

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How to Make

1. Make the Caramelized Onions

1. Heat butter or oil in a large skillet over medium heat.
2. Add the sliced onions and a pinch of salt.
3. Cook low and slow for 25-35 minutes, stirring occasionally, until deep golden brown and soft.
4. Optional: add coconut aminos during the last minute of cooking.
5. Set aside.

2. Make the Mashed Potatoes

1. Bring a large pot of water to a boil.
2. Add potato chunks to the water and cook 12-15 minutes or until fork-tender.
3. Drain well and return potatoes to the pot.
4. Add butter, Boursin, sour cream, and salt and pepepr. Mash until smooth.
5. Add milk a splash at a time, only if you prefer to loosen the consistency.
6. Adjust the salt and pepper to taste.

3. Assemble & Melt the Cheese

1. Transfer mashed potatoes to a baking dish or serving dish that can go under the broiler.
2. Spread caramelized onions evenly over the top.
3. Sprinkle shredded cheese over the onions.
4. Broil 1-3 minutes until the cheese melts and bubbles (watch closely!).

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Storage & Reheating

• Store leftovers in an airtight container up to 3-4 days.
• Reheat in the oven at 350°F in a covered oven safe dish, or warm on the stove with a splash of milk.
• The topping reheats beautifully and gets even more flavorful the next day.

More Delicious Holiday Sides

• Gluten Free Green Bean Casserole
• Paleo Gravy

Did you try this recipe? Let me know in the comments below how it came out for you!