French Onion Potato Bake

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A simple French onion potato bake that uses Yukon potatoes, French onion soup mix, and Gruyere cheese to create a cheesy, creamy casserole!

Onion soup mix has a lot of uses. In fact, we have a French onion dip recipe that uses it as a spice blend.

For today, we’re using that handy soup mix to create Kim’s French onion potato bake.

As you can imagine, this side dish features cheesy, comforting potatoes flavored with those savory spices.

A scoop of the french onion potato bake on a plate.
We garnished our potato casserole with sliced green onion.

How to make a French onion potato bake with soup mix?

Creating this potato casserole isn’t difficult, but it does have quite a few steps.

To make things easier, I separated out the instructions into sections.

That way, you can easily follow along with our directions. So, shall we get started?

An aerial view of the casserole in a baking dish.
You only need a small baking dish for this recipe.

Prep the Potatoes:

First, start by boiling the potatoes in a large stockpot filled with water. Use high heat for the quickest results.

The potatoes will need to boil for 12-15 minutes or until they’re fork tender.

Meanwhile, preheat your oven to 350 degrees F. and grease an 8×8-inch square baking dish with non-stick cooking spray.

Once the potatoes are done, remove them from the heat and transfer them to an ice bath.

Let the taters chill until they’re cool enough to handle.

Afterward, peel the potatoes and slice them into 1/2-inch circular pieces. Set them aside for now.

Butter, heavy cream, and soup mix in a skillet.
You can make the sauce while the potatoes boil.

Make the Cheese Sauce:

Next, place a medium skillet over low-medium heat. Place the butter into the pan and let it melt.

After that, whisk in the flour and let it cook for 2-3 minutes to create your roux.

Now, while whisking continuously, pour in the heavy cream and milk. Go ahead and stir in the onion soup mix.

Then, when the liquid begins to steam, start adding the shredded Gruyere cheese.

I recommend sprinkling in 1 handful of cheese at a time. Whisk the mixture until the Gruyere has melted.

Continue the process until you’ve added all the shredded cheese to the sauce. Then remove the skillet from the heat.

Sliced onions and boiled potatoes layered in a baking dish.
Peeling the potatoes is optional. Feel free to leave the skins on if you wish.

Build the Casserole:

It’s time to begin layering your potatoes, onions, and sauce into the baking dish. Kim placed 1/3 of each ingredient into every layer.

So, it goes sliced potatoes, onions, and then cheese sauce. Repeat the same process over and over again until the ingredients are gone.

Part of the sauce poured over the potatoes and onions.
White cheddar also makes a great cheese sauce for this dish.

Bake the Casserole and Serve:

To finish off the casserole, she added more shredded Gruyere cheese.

Last, place the potato bake into the oven (uncovered) and let it cook for about 30-minutes until the potatoes are cooked through.

The casserole topped with shredded gruyere cheese.
At this point, you could top the casserole with breadcrumbs for a crispy topping.

Remove the casserole from the oven and let it cool for a few minutes before serving.

That’s it, your French onion potato bake is done! Kim and I hope you enjoy it and wish you all the best 🙂

The potato side dish has baked and needs to cool.
Let it cool a little before serving; otherwise, it won’t hold together.

Recipe Tips:

  • If you don’t have a digital kitchen scale, then 2 pounds of Yukon potatoes comes out to about 12 small potatoes or 6-8 medium potatoes.
  • Whether you make 2 or 3 layers for this casserole is up to you. In fact, if you’re using a large casserole dish, then you may only have 1-2 layers.
  • The amount of layers in the dish may effect the baking time. Be sure to keep an eye on the casserole as it bakes; otherwise, it may scorch.
A serving of casserole removed to show the inner layers.
Who knew French onion soup mix could make such a tasty side dish?

Don’t forget to check out our Cheesy French Onion Potato Bake web story!

A serving of the french onion potato bake on a plate.

French Onion Potato Bake

4.5 from 6 votes
Print Pin
Author: Kimberly
Prep Time: 30 minutes
Cook Time: 45 minutes
Additional Time: 10 minutes
Total Time: 1 hour 25 minutes
Servings: 16 Servings


  • 2 pounds gold potatoes
  • 3 tablespoons unsalted butter
  • 3 tablespoons all-purpose flour
  • 1 cup heavy cream
  • ½ cup whole milk
  • 1 ounce onion soup mix, 1 packet
  • 1 ½ cups Gruyere cheese, shredded off the block
  • 1 ½ cups white onion, thinly sliced


  • Preheat the oven to 350°F, and grease an 8 x 8, 9 x 9 – inch, or 2.5 quart baking dish. Set aside.
  • Bring a large pot of lightly salted water and potatoes to a boil. Cook until the potatoes are just barely fork tender, about 12 to 15 minutes . Drain the water, and transfer the potatoes to an ice bath. When they’re cool enough to handle, gently remove the skins, and slice into ¼ – inch thick slices.
    2 pounds gold potatoes
  • While the potatoes cook, make the sauce. Heat a medium skillet over low to medium heat. Add the butter, and allow it to melt. Once melted, add the flour. Whisk for 2 to 3 minutes, then while whisking, add the heavy cream and milk. Continue to whisk until smooth, then pour in the onion soup mix. Whisk to combine.
    3 tablespoons unsalted butter
    3 tablespoons all-purpose flour
    1 cup heavy cream
    ½ cup whole milk
    1 ounce onion soup mix
  • When the mixture begins to thicken slightly and steam, slowly begin to add 1 cup of the cheese, whisking between each addition. Remove from heat.
  • Place a third of the potatoes into the baking dish, followed by a third of the onions. Top with a third of the cheese sauce. Repeat with the remaining potatoes, onions, and cheese sauce, then sprinkle the remaining ½ cup of cheese over the top.
    1 ½ cups white onion
  • Bake uncovered for 25 to 30 minutes or until the potatoes are cooked through. Serve hot, and store leftovers in the refrigerator for 3 days.


The calories listed are an approximation based on the ingredients in the recipe card and a serving size of 1/2-cup of the French onion potato bake. Actual calories will vary.
For more information and tips, please refer to the post.


Serving: 0.5cup | Calories: 185kcal | Carbohydrates: 14g | Protein: 6g | Fat: 12g | Saturated Fat: 7g | Polyunsaturated Fat: 1g | Monounsaturated Fat: 3g | Trans Fat: 0.1g | Cholesterol: 37mg | Sodium: 258mg | Potassium: 311mg | Fiber: 2g | Sugar: 2g | Vitamin A: 416IU | Vitamin C: 12mg | Calcium: 158mg | Iron: 1mg

Nutrition Disclaimer

Kim and John Vargo of Berly’s Kitchen and its affiliates are not dieticians or nutritionists. Any nutritional information shared is an estimate. If preferred, use your favorite online nutrition calculator to double check the amounts. Calories and other nutritional values can vary based on brand and serving size.

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    1. LOL! That’s awesome Betty! We’re glad you like the sauce and we hope the rest of the recipe comes out as expected. Have a wonderful day 🙂

4.50 from 6 votes (5 ratings without comment)

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