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Updated: Nov 29, 2025 · Published: Apr 14, 2025 by The Savory Tart · This post may contain affiliate links · 1 Comment

Mashed Potatoes au Gratin (Pommes Mont d’Or)

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While my Mashed Potatoes au Gratin originally evolved from repurposing leftover holiday mashed potatoes, those aren't always at one's fingertips. And when they aren't, I turn to prepared refrigerated mashed potatoes to pull this together in no time at all -- it's the quintessential quick, easy and elegant side-dish with prep done in a matter of minutes.

Mashed Potatoes au Gratin | Pommes Mont d’Or in Gratin dish

Potatoes au Gratin | Pommes Mont d’Or: They are a standard in France where they are known as Pommes Mont d'Or which translates to "Golden Mountain of Potatoes". It is a traditional dish featuring mashed potatoes combined with eggs and cheese creating a divinely light and fluffy soufflé-like dish with a crispy golden brown crusty top.

I need to move this higher up in my repertoire of recipes. It's perfect on a holiday table served next to spiral ham or a roast beef -- or served for a weeknight meal alongside a purchased roast chicken and steamed vegetables.

And not only is it gluten free, kids love what are essentially cheesy mashed potatoes!

Ingredients

Mashed Potatoes au Gratin | Pommes Mont d’Or Ingredients
  • butter
  • mashed potatoes
  • large eggs
  • Gruyere, Swiss or Comte cheese
  • salt
  • ground black pepper
  • nutmeg

See recipe card for quantities.

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Instructions

Buttered Gratin dish

Preheat the oven to 400F. Set oven rack to lower middle position.Butter a shallow gratin dish or baking dish. 

Eggs whisked in bowl

Whisk the eggs in a medium bowl. (Use an immersion blender if desired.) 

Ingredients in bowl

Add the potatoes and one cup of the grated cheese, salt, pepper and nutmeg.

Ingredients combined

Stir to combine.

Ingredients in prepared gratin dish

Transfer potato mixture to the prepared dish, smoothing top. Sprinkle remaining cheese evenly over the top and place in oven. 

Baked Mashed Potatoes au Gratin | Pommes Mont d’Or

Bake until the gratin is puffed and the top is golden, about 30 to 35 minutes, 

Hint: It's not just a hint, it's a confession. "Bob Evans" makes solid mashed potatoes that are sold prepared in the refrigerator section of the grocery store.

The "family size" has the exact amount needed to make my Mashed Potato Gratin and have use them countless times. ("Bob" also "makes" a Sour Cream and Chive variety that is sure tasty in this recipe too.)

Mashed Potatoes au Gratin | Pommes Mont d’Or side view

Substitutions

  • Gruyere Cheese - There are a variety of cheeses that can be substituted here including Swiss, Comte and Gouda. Even an aged cheddar (but leave out the nutmeg).
  • Leftover Mashed Potatoes - Substitute prepared refrigerated or frozen mashed potatoes if you don't have leftover.
  • Gluten Free - This is a great option for a gluten free side dish -- just make sure the prepared mashed potatoes are gluten free.

Variations

  • Bacon - dice six strips of cooked bacon and add into the mashed potato mixture
  • Caramelized Onions -- caramelize a diced small yellow onion and add to the mashed potato mixture before baking
  • Extra Fluffy -- add an extra egg -- this will require baking just a little bit longer
  • Chives - stir in 2 tablespoons of minced chives to the potato mixture before baking
  • Mushrooms - stir in ¾ cup diced cooked mushrooms that have been sautéed in butter or olive oil
Mashed Potatoes au Gratin | Pommes Mont d’Or overhead view

Equipment

  • gratin dish or small casserole dish
  • whisk or immersion blender
  • medium bowl

Storage

This is by far the best served immediately while it is still fluffy and shuffle-like.

Mashed Potatoes Gratin can be safely stored in the refrigerator for 3 to 5 days after baking. Allow to rest at room temperature for 30 minutes prior to reheating.

You can also freeze the baked gratin safely for up to 2 to 3 months in the freezer. Thaw completely before reheating.

Mashed Potatoes au Gratin | Pommes Mont d’Or scooped

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🍽️ Recipe

Mashed Potatoes au Gratin | Pommes Mont d’Or

Mashed Potatoes au Gratin | Pommes Mont d’Or

The Savory Tart
This traditional French dish features leftover or prepared mashed potatoes combined with eggs and cheese creating a divine light and fluffy soufflé-like dish with a crispy golden brown crusty top. So quick to prepare too!
5 from 1 vote
Print Recipe Pin Recipe
Prep Time 10 minutes mins
Cook Time 30 minutes mins
Total Time 40 minutes mins
Course Side Dish
Cuisine American, French
Servings 8

Equipment

  • gratin dish or small casserole dish
  • whisk or immersion blender
  • medium bowl

Ingredients
  

  • butter
  • 6 cups mashed potatoes
  • 4 large eggs
  • 1-⅓ cups grated Gruyere, Swiss or Comte about 6 ounces, divided
  • ½ teaspoon salt
  • fresh ground black pepper
  • 1 pinch fresh grated nutmeg

Instructions
 

  • Butter a shallow baking dish or casserole.
  • Preheat the oven to 400F. Set oven rack to lower middle position.
  • Butter a shallow gratin dish or baking dish. Whisk the eggs in a medium bowl. (Use an immersion blender if desired.) Add the potatoes and one cup of the grated cheese, salt, pepper and nutmeg. Stir to to combine.
  • Transfer potato mixture to the prepared dish, smoothing top. Sprinkle remaining cheese evenly over the top and place in oven.
  • Bake until the gratin is puffed and the top is golden, about 30 to 35 minutes,
  • Serves 6.
Keyword fluffy mashed potatoes, leftover mashed potatoes, Mashed Potatoes, pommes mot d'or, potato casserole, Potato Gratin, Potato Souffle, Potatoes au Gratin, quick and easy, thanksgiving leftovers

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Reader Interactions

Comments

  1. Shawn Webb says

    December 30, 2025 at 5:30 pm

    5 stars
    I made a double batch for Christmas, and my guests went crazy over them! So easy!

    Reply

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