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Layers of thinly sliced potatoes, caramelized onions, and cheese being assembled for a savory potato casserole.

French Onion Potato Bake: The Ultimate Cheesy & Savory Casserole

Indulge in the ultimate comfort food with this French Onion Potato Bake recipe. Layers of tender potatoes, deeply caramelized onions, and rich Gruyère cheese bake into a savory, irresistible casserole perfect for any occasion.
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Prep Time 25 minutes
Cook Time 1 hour 5 minutes
Total Time 1 hour 30 minutes
Servings: 8 servings
Course: Main Course, Side Dish
Cuisine: American, French
Calories: 450
Ingredients Equipment Method Notes

Ingredients
  

Main Ingredients
  • 3 lbs Yukon Gold or Russet potatoes peeled and sliced 1/8-inch thick
  • 2 large yellow onions thinly sliced
  • 4 tbsp unsalted butter
  • 2 cloves garlic minced
  • 1 tsp fresh thyme leaves
  • 1.5 cups beef broth low-sodium
  • 1 cup heavy cream
  • 2 cups Gruyère cheese shredded
  • 0.5 cup Parmesan cheese grated
  • 1 tsp salt or to taste
  • 0.5 tsp black pepper freshly ground

Equipment

  • 1 9x13 inch baking dish
  • 1 Large Skillet
  • 1 Mandoline Slicer Optional, but recommended for even slices.

Method
 

  1. Melt butter in a large skillet over medium-low heat. Add sliced onions and cook slowly for 30-40 minutes, stirring occasionally, until deeply golden brown and sweet. Add minced garlic and thyme in the last minute of cooking.
  2. Preheat oven to 400°F (200°C). Grease a 9x13 inch baking dish. While onions cook, peel and thinly slice potatoes.
  3. In a large bowl, whisk together the beef broth and heavy cream. Season with salt and pepper.
  4. Arrange 1/3 of the potatoes in the baking dish. Top with 1/3 of the onions and 1/3 of the Gruyère. Pour 1/3 of the cream mixture over the top. Repeat for two more layers.
  5. Finish with the remaining Gruyère and sprinkle with Parmesan cheese.
  6. Cover the dish tightly with foil and bake for 45 minutes.
  7. Remove the foil and bake for an additional 15-20 minutes, until the top is golden and bubbly and the potatoes are tender.
  8. Let the casserole rest for 10-15 minutes before serving to allow the sauce to set.

Notes

Tip 1: Don't rush the caramelization process for the onions; low and slow heat develops the best flavor.
Tip 2: Use a mandoline slicer for uniform potato slices to ensure even cooking.
Tip 3: Shred your own cheese from a block for the creamiest, meltiest results.