Sauteed mushrooms and flavorful caramelized onions meet scalloped potatoes in this hearty holiday side dish! – These caramelized onion scalloped potatoes are always a dinner favorite.
Side dish STRONG is how you want to be rolling into the holiday season! These scalloped potatoes are the only way to do that.
Name a list of ways you could go wrong with potatoes and lots of cheese. I don’t really think there’s even one.
Throw caramelized onions and mushrooms into the party and I think we’ve got ourselves a holiday winner.
A bubbly, cheesy pan of that goodness up there is pretty much Thanksgiving + Christmas essentials in my book and just one of those things that should be taking up roughly half of your dinner plate.
Cause we all know side dishes are the REAL star, let’s be honest.
These Caramelized Onion Scalloped Potatoes feature…
- Perfectly tender sliced potatoes in a rich cream sauce
- Gooey swiss cheese and gruyere cheese
- Flavorful caramelized onions and mushrooms
Making the Caramelized Onion Scalloped Potatoes
(scroll down to the bottom of post for the full recipe)
Ingredients You Will Need
- Yukon gold potatoes
- Sweet onion
- Button mushrooms
- Unsalted butter
- Heavy whipping cream
- All-purpose flour
- Fresh thyme
- Swiss cheese
- Gruyere cheese
Choosing Your Potatoes
We recommend using Yukon golds or yellow potatoes for this recipe. These are typically creamier, fluffier potatoes that cook up particularly well in a rich dish like scalloped potatoes.
If you don’t have access to Yukon golds, russet potatoes would work fine, just be aware they might not be as rich!
Tips for Perfect Scalloped Potatoes
- Slice potatoes thin – if you have access to a mandoline, this makes the job much easier! (just be VERY careful not to cut yourself) Otherwise a sharp knife will work fine too.
- Caramelize onions slowly – cook the onions low ‘n’ slow over medium heat until a deep caramelized brown, about 20 minutes.
- Make cream sauce – we’re going to make a quick cream sauce which will be the sauce base the potatoes will bake in.
- Layer scalloped potatoes – we’re going to layer the scalloped potatoes in three layers of sliced potatoes, cream sauce, and caramelized onions/mushrooms.
- Use two kinds of cheeses – swiss cheese and a rich gruyere are an incredible cheese duo in these potatoes. Sprinkle the cheese generously on top of potatoes.
- Bake covered first, then remove and continue baking to brown top – cover the pan tightly with foil and bake 40 minutes. Then, remove the foil and continue baking an additional 25-30 minutes until the potatoes are tender and the cheese is browned.
- Let scalloped potatoes sit before serving to set – it can be tempting to dig into the potatoes straight out of the oven but be patient and let them sit 15 minutes before digging in so the potatoes can set a bit.
There’s a few different ways you can make this recipe a little different!
- Try another cheese – a mild cheddar, smoked gouda, provolone, or low-moisture mozzarella would be great substitutes for the swiss + gruyere combo. Just pick your favorites!
- Skip the mushrooms – if you’re not a fan of mushrooms, feel free to skip them or sub in another veggie.
- Try another herb – rosemary or fresh parsley would be great in place of the thyme.
This is just the GOOD side dish stuff, guys. The potatoes are incredibly rich, creamy, loaded with flavor from the caramelized onions + mushrooms, and perfectly cheesy.
They just might be the only convincer you need to ditch the mashed potatoes this year and join the scalloped potatoes gang. Promise it’s nice here!
Save this recipe using the ‘save to recipe box’ button below. If you make it, please let us know! Leave a comment + star rating below, or take a photo and tag it on Instagram with #wholeandheavenlyoven
More potato dishes to try out next!
- Air Fryer Fingerling Potatoes
- Roasted Garlic Butternut Squash Scalloped Potatoes
- Skillet Creamy Tuscan Salmon and Baby Potatoes
Mushroom Caramelized Onion Scalloped Potatoes
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- 3 tablespoons unsalted butter, divided
- 1 large sweet vidalia onion, thinly sliced
- 8 oz button mushrooms, thinly sliced
- 2 medium cloves garlic, minced
- 2 tablespoons all-purpose flour
- 1-1/2 cups milk
- 1/4 cup heavy whipping cream
- 1 tablespoon minced fresh thyme
- Salt and pepper to taste
- 3 lbs yukon gold potatoes, peeled and cut into 1/8-in thick slices
- 1 cup shredded Swiss cheese
- 1 cup shredded Gruyere cheese
- In a large skillet over medium heat, melt 1 tablespoon butter and swirl pan to evenly coat. Add onions and cook over medium heat, stirring occasionally until onions are a deep golden brown, about 20 minutes.
- Increase heat to medium-high and stir mushrooms and garlic into onions. Cook an additional 2-3 minutes until mushrooms are lightly browned. Remove onions and mushrooms from pan and set aside.
- In same skillet over medium heat, melt remaining 2 tablespoons butter then whisk flour in until smooth. Cook 1-2 minutes until flour-butter mixture is golden brown.
- Slowly begin to add milk and cream, whisking constantly until sauce is smooth. Bring sauce to a simmer over medium heat and cook until slightly thickened. Remove from heat and add thyme and season with salt and pepper to taste.
- Preheat oven to 375F and grease a 9×13 baking pan. Layer 1/3 of sliced potatoes in bottom of pan overlapping them slightly. Top with 1/3 cream mixture and 1/3 caramelized onions/mushrooms. Repeat layers two more times and sprinkle top with Swiss and Gruyere cheeses.
- Cover pan tightly with tin foil and baked scalloped potatoes at 375F 40 minutes. Remove tin foil and continue baking an additional 25-30 minutes until potatoes are tender, bubbly and top is a deep golden brown. Let potatoes stand 15 minutes before serving warm. Enjoy!