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A close-up shot of the cheesy potato bake, with a serving spoon lifting a portion to show the creamy layers of potato and caramelized onions.

French Onion Potato Bake: The Ultimate Cheesy & Savory Casserole

Discover the ultimate comfort food with this French Onion Potato Bake. Layers of tender potatoes, deeply caramelized onions, and nutty Gruyère cheese create a rich, savory, and unforgettable casserole perfect for any occasion.
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Prep Time 20 minutes
Cook Time 1 hour
Total Time 1 hour 20 minutes
Servings: 8 servings
Course: Main Course, Side Dish
Cuisine: American, French
Calories: 450
Ingredients Equipment Method Notes

Ingredients
  

Main
  • 2.5 lbs Yukon Gold potatoes peeled and sliced 1/8-inch thick
  • 3 tbsp Unsalted Butter
  • 1 tbsp Olive Oil
  • 3 Large Yellow Onions thinly sliced
  • 2 cloves Garlic minced
  • 1 tsp Fresh Thyme Leaves
  • 1/4 cup Dry White Wine optional, like Sauvignon Blanc
  • 1.5 cups Heavy Cream
  • 1 cup Beef Broth
  • 1.5 tsp Salt
  • 1/2 tsp Black Pepper freshly ground
  • 2 cups Gruyère Cheese shredded

Equipment

  • 1 9x13 inch Baking Dish
  • 1 Large Skillet
  • 1 Mandoline slicer (optional)

Method
 

Main
  1. In a large skillet over medium-low heat, melt butter and olive oil. Add onions and a pinch of salt. Cook, stirring occasionally, for 30-40 minutes until deep golden brown and jammy. Add garlic and thyme and cook for 1 more minute. Deglaze with white wine, if using, and simmer until evaporated.
  2. Preheat oven to 400°F (200°C). Butter a 9x13 inch baking dish. Slice potatoes thinly and uniformly.
  3. In a large bowl, whisk together heavy cream, beef broth, salt, and pepper.
  4. Layer one-third of the potatoes in the baking dish. Top with half the onions and one-third of the cheese. Repeat the layers. Finish with the last layer of potatoes.
  5. Pour the cream mixture evenly over the potatoes. Top with the remaining cheese. Bake for 50-60 minutes until potatoes are tender and the top is golden and bubbly.
  6. Let the bake rest for 10 minutes before serving to allow the sauce to set.

Notes

Using a mandoline slicer ensures your potatoes cook evenly.
Don't rush the onion caramelization; it is the key to the dish's deep flavor.
Feel free to substitute Gruyère with a sharp white cheddar or a mix of Swiss and Parmesan cheese.