The Ultimate French Onion Mashed Potatoes

Jump to Recipe

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.

Serving these for Thanksgiving? Use the leftovers in my Thanksgiving Egg Rolls! I also love swapping leftover turkey in my Gluten Free Chicken Divan!

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

---

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.

---

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!).

---

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!