Cheesy French Onion Potato Bake
This French onion potato bake layers tender Yukon Gold potatoes, sliced onions, and a creamy Gruyere cheese sauce flavored with onion soup mix. It’s everything I love about French onion soup in casserole form.
If you’ve ever made a potato bake that came out watery or crunchy in the middle, this recipe fixes both problems.
The potatoes get boiled until fork tender before they’re layered into the dish. So there’s no guessing whether the slices cooked through, and no mandoline required.
The sauce starts with a roux, which keeps it thick and creamy instead of thin and soupy. It’s the same method I use for my scalloped potatoes, and it works every time.
A packet of French onion soup mix adds a ton of flavor. There’s no caramelizing onions for an hour and no homemade stock. Just creamy, cheesy potatoes.
Tips for the Best Potato Bake
Boil the potatoes until just fork tender. They’ll finish cooking in the oven. If they’re too soft going in, they can turn mushy.
Add the Gruyere one handful at a time. Dumping it all in at once can make the sauce grainy. Let each handful melt before adding the next.
Keep the heat low when making the sauce. High heat is the fastest way to break a cheese sauce.
Bake it uncovered. This helps the top brown and keeps extra moisture from collecting in the dish.
How to Make a French Onion Potato Bake
Add the potatoes to a large stockpot, cover them with water, and boil for 12 to 15 minutes until fork tender.
While they cook, preheat the oven to 350°F and grease an 8×8-inch baking dish.
Transfer the potatoes to an ice bath. Once they’re cool enough to handle, peel them and slice them into 1/4-inch rounds.
Next, melt the butter in a skillet over low-medium heat. Whisk in the flour and cook for 2 to 3 minutes to make a roux.
While whisking, slowly pour in the heavy cream and milk. Stir in the onion soup mix.
When the liquid starts to steam, add the Gruyere a handful at a time. Whisk until each handful melts before adding more. Then remove the pan from the heat.
Layer a third of the potatoes, a third of the sliced onions, and a third of the sauce into the dish. Repeat until everything’s used.
Top with extra shredded Gruyere. Bake uncovered for 25 to 30 minutes until the cheese is melted and the edges are bubbly.
Let the bake rest for a few minutes before serving. It thickens a little as it cools.
Storage and Reheating
Store leftovers in an airtight container in the fridge for up to 3 days.
Reheat single servings in the microwave in short bursts. For larger amounts, cover the dish with foil and warm it in a 350°F oven until heated through.
I don’t recommend freezing this one. Cream-based sauces tend to separate after thawing.
Ingredients
- 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
💌 Don't forget to save this recipe!
Instructions
- Preheat the oven to 350°F, and grease an 8×8-inch, 9×9-inch, or 2.5-quart baking dish. Set aside.
- Bring a large pot of lightly salted water and the 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 let it melt. Whisk in the flour and cook for 2 to 3 minutes. While whisking, add the heavy cream and milk. Whisk until smooth, then stir in the onion soup mix.3 tablespoons unsalted butter3 tablespoons all-purpose flour1 cup heavy cream½ cup whole milk1 ounce onion soup mix
- When the mixture starts to thicken and steam, slowly add 1 cup of the cheese a handful at a time, whisking between each addition. Remove from heat.1 ½ cups Gruyere cheese
- 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 sauce. 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. Let the bake rest for a few minutes before serving.
Notes
- Shred the Gruyere off the block. Pre-shredded cheese doesn’t melt as smoothly.
- Add the cheese slowly so the sauce stays smooth.
- Store leftovers in the refrigerator for up to 3 days. Freezing isn’t recommended. The cream sauce may separate after thawing.
- The calories listed are an approximation based on the ingredients in the recipe card and a serving size of 1 cup. Actual calories will vary.
Nutrition
The sauce is so good! I’m not even done making this and i keep “tasting” the sauce.
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 🙂