Looking for the perfect side to elevate your holiday feast? Our French Onion Au Gratin Potatoes are rich, creamy, and packed with caramelized onion flavor, making them an irresistible addition to any meal. They pair beautifully with holiday roasts like Standing Prime Rib, Roast Leg of Lamb, or Glazed Cornish Hens, adding a comforting, cheesy touch that will have everyone asking for seconds.
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🥔 The Ingredients
This recipe combines savory aromatics, rich cheeses, and tender potatoes to create a deeply flavorful and comforting side dish. Find ingredient notes (including substitutions and variations) below.
📝 Ingredients Notes and Substitutions
- Yellow Onions: Sweet and mellow when caramelized; you can substitute with white or Vidalia onions for a slightly different flavor.
- White Wine: Adds depth and acidity; if you prefer, substitute with extra beef broth or a splash of apple cider vinegar.
- Beef Broth: Provides rich, savory flavor; chicken broth or vegetable broth can be used as a milder alternative.
- Gruyère Cheese: Melts beautifully with a nutty flavor; Swiss or Emmental cheeses are great substitutes if needed.
- Parmesan Cheese: Adds sharpness and umami; Pecorino Romano or Asiago can be used instead.
- All-Purpose Flour: Used to thicken the sauce; gluten-free flour blends or cornstarch can be substituted for gluten-free versions.
- Dried Thyme: Adds earthy, herbal notes; fresh thyme can be used (about twice the amount), or substitute with rosemary or savory for a different herbal twist.
See the recipe card (with video) below for a full list of ingredients and measurements.
🔥 Tips and Tricks for the Perfect Side Dish
- Caramelize onions slowly: Cook the onions over medium-low heat to develop a deep, sweet flavor without burning.
- Use thin potato slices: Thin, even slices ensure the potatoes cook through evenly and absorb the sauce well. A mandolin slicer makes this easy.
- Layer ingredients evenly: Distribute the onions, sauce, and cheese evenly between layers for balanced flavor in every bite.
- Don’t skip the wine: Even though optional, white wine adds a subtle acidity that brightens the rich sauce.
- Let the dish rest: Allow the casserole to rest for 10-15 minutes after baking, so it sets and slices cleanly.
- Use freshly shredded cheese: Freshly shredded Gruyère and Parmesan melt better and provide superior flavor compared to pre-shredded varieties.
- Adjust seasoning at the end: Taste the sauce before baking and adjust salt and pepper as needed for the best flavor.
👩🏼🍳 How to Make French Onion au Gratin Potatoes
- Step 1: Melt the butter in a large pot and stir in the sliced onions to coat.
- Step 2: Cook the onions, stirring often, until reduced, caramelized, and brown (not burnt). Stir in the garlic and thyme and cook for another minute.
- Step 3: Add the wine and cook until mostly evaporated, about 1 minute.
- Step 4: Stir in the flour and cook for another minute, stirring often.
- Step 5: Whisk in the cream and stock (or broth) and stir until slightly thickened, about 3 minutes.
- Step 6: Add a layer of potatoes to the greased pan. Sprinkle with a little salt and pepper, and then top with a thin layer of the sauce and a sprinkle of Parmesan cheese. Repeat until potatoes are all used.
- Step 7: Top with shredded Gruyere cheese.
- Step 8: Cover with foil and bake for 45 minutes in a 375°F oven. Remove the foil and bake another 15 to 20 minutes. Let it rest for at least 10 to 15 minutes.
🍽️ How to Serve
- Serve warm and bubbly straight from the oven for the best creamy, cheesy texture. However, remember to let the potatoes rest for at least 10 to 15 minutes before slicing. The dish will stay warm (covered with foil) for up to 30 minutes.
- Pair beautifully with roast beef tenderloin, herb-stuffed pork loin, or maple-glazed turkey breast for a complete, elegant meal.
- Garnish with fresh thyme or chopped parsley to add a pop of color and fresh herbal aroma.
- Offer alongside glazed baby carrots or roasted cauliflower with olives to balance the richness.
- Serve on individual plates or in a large casserole dish for family-style dining.
🙋🏽♂️ Frequently Asked Questions
Can I make French Onion Au Gratin Potatoes ahead of time?
Yes, you can prepare the dish a day in advance and refrigerate it. Just bake it freshly before serving for the best texture and flavor.
What type of potatoes work best for French Onion Au Gratin Potatoes?
Yukon Gold or other waxy potatoes (ie, red, fingerling, or new) are ideal because they hold their shape well and absorb the sauce beautifully.
Can I use a different cheese in French Onion Au Gratin Potatoes?
Absolutely! Swiss, Emmental, or even a sharp white cheddar are great alternatives if you don’t have Gruyère or Parmesan.
Is the white wine necessary in French Onion Au Gratin Potatoes?
The wine adds depth and brightness, but you can omit it and substitute it with extra broth or a splash of vinegar if preferred.
Can French Onion Au Gratin Potatoes be made gluten-free?
Yes, you can substitute the all-purpose flour with a gluten-free flour blend or cornstarch to thicken the sauce.
😋 Other “Special Occasion” Side Dishes
Ready to make a show-stopper side dish for your special feast? Go for it!
And when you do, be sure to take a photo of it, post it on Instagram, and tag @HowToFeedaLoon and hashtag #HowToFeedaLoon!
French Onion au Gratin Potatoes
Rich, creamy, and loaded with caramelized onions and melted cheese, these French Onion Au Gratin Potatoes make a comforting and elegant side dish perfect for any special meal.
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Servings: 8
Calories: 413kcal
Video
Equipment
- Large pot or skillet for caramelizing onions (8-quart Dutch oven is excellent)
- 9"x13" baking dish or similar size baking dish or 12-inch cast-iron skillet
Ingredients
- 4 tablespoon unsalted butter
- 4 large yellow onions or 5 medium, peeled and thinly sliced
- 4 cloves garlic minced
- 1 teaspoon dried thyme or 1 tablespoon fresh
- ¼ cup white wine optional, see NOTES
- 3 tablespoon all-purpose flour
- 2 cups beef stock or broth
- 1 cup heavy cream or half and half
- salt and pepper
- 1 tablespoon oil or butter, for greasing dish
- 2½ lbs gold potatoes peeled and thinly sliced (⅛" inch)
- ¼ cup Parmesan cheese grated
- 1 cup Gruyère cheese shredded
- fresh thyme chopped, for garnish (optional)
Instructions
- In a large skillet, pot, or Dutch oven, melt the butter over medium heat. Add the onions, and cook, stirring often, until deep golden brown, and caramelized – about 40 to 50 minutes. Stir in the garlic and thyme and cook, stirring often, for another minute.4 tablespoon unsalted butter, 4 large yellow onions, 4 cloves garlic, 1 teaspoon dried thyme
- Add the wine (if using) and stir until mostly evaporated, usually about 1 minute. Stir in the flour to coat the onions and cook, stirring often, for another 1 to 2 minutes.¼ cup white wine, 3 tablespoon all-purpose flour
- Whisk in the beef stock and cream. Gently stir with a wooden spoon or spatula until slightly thickened, about 3 to 4 minutes. Stir in 1 teaspoon salt and ½ teaspoon black pepper. Remove from the heat.2 cups beef stock, 1 cup heavy cream, salt and pepper
- Preheat oven to 375°F.
- Grease your dish with softened butter or olive oil. Arrange a double layer of potatoes in the greased dish. Sprinkle salt and pepper over the potatoes. Spoon a thin layer of the sauce over the potatoes (you'll do about a quarter of the sauce). Sprinkle Parmesan cheese over the sauce. Repeat this process 3 to 4 more times (until you run out of potatoes, or sauce, whichever comes first).1 tablespoon oil, 2½ lbs gold potatoes, ¼ cup Parmesan cheese
- Top the dish with the shredded Gruyère. Cover with foil and bake in the preheated oven (375°F) for 45 minutes. Remove the foil and bake for another 20 minutes, or until the cheese has browned in spots.1 cup Gruyère cheese
- Remove the dish from the oven and let rest for 10 to 15 minutes. Or, cover with foil and let rest for up to 30 minutes. Garnish with chopped fresh herbs (ie, thyme), if desired. Serve immediately.fresh thyme
Notes
NOTE: Watch the video in the recipe card for visual guidance.
- For best flavor, use dry white wine, but it can be omitted or replaced with extra broth or a splash of vinegar.
- Store leftovers in an airtight container in the refrigerator for up to 3 days. Reheat gently in the oven until warmed through.
- This dish freezes well—cool completely, then freeze in an airtight container for up to 2 months. Thaw overnight in the fridge before reheating. The texture may be a little grainy after thawing, but will still be delicious after reheating.
- Use thinly sliced potatoes for even cooking and a creamy texture.
- Freshly shredded cheese melts better than pre-shredded varieties.
Nutrition
Calories: 413kcal | Carbohydrates: 36g | Protein: 12g | Fat: 25g | Saturated Fat: 14g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 7g | Trans Fat: 0.2g | Cholesterol: 69mg | Sodium: 308mg | Potassium: 879mg | Fiber: 5g | Sugar: 6g | Vitamin A: 802IU | Vitamin C: 34mg | Calcium: 270mg | Iron: 2mg
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Wes says
This is my new favorite holiday side dish! 5,000,000% Loon APPROVED!
Kris Longwell says
Woo hoo!!!!!