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French Onion Potato Casserole 1

French Onion Potato Casserole

This French Onion Potato Casserole combines the rich, caramelized essence of French onion soup with the creamy comfort of a potato casserole. Featuring layers of thinly sliced potatoes nestled in a savory French onion-infused sauce and topped with bubbly, golden cheese, this recipe delivers restaurant-quality flavors right from your home oven.
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Prep Time 25 minutes
Cook Time 55 minutes
Resting Time 10 minutes
Total Time 1 hour 20 minutes
Course Side Dish
Cuisine American, French
Servings 10 servings
Calories 310 kcal

Equipment

  • 9x13-inch Baking Dish
  • Mandoline slicer (optional but recommended)
  • Large Skillet

Ingredients
  

For the Base

  • 3 pounds russet potatoes thinly sliced (about 1/8 inch thick)
  • 2 large sweet onions thinly sliced
  • 3 tablespoons butter
  • 2 tablespoons olive oil
  • 2 cloves garlic minced
  • 1 tablespoon fresh thyme leaves or 1 teaspoon dried
  • 1 teaspoon sugar helps with onion caramelization
  • 2 cups beef broth can substitute vegetable broth for vegetarian option
  • 1 cup heavy cream
  • 2 tablespoons all-purpose flour
  • 1 teaspoon salt
  • 1/2 teaspoon black pepper

For the Topping

  • 1 1/2 cups gruyère cheese shredded (can substitute Swiss cheese)
  • 1 cup crispy fried onions
  • 2 tablespoons fresh parsley chopped (for garnish)

Instructions
 

  • Preheat your oven to 375°F (190°C) and grease a 9x13 inch baking dish. Wash and peel the potatoes, then slice them thinly using a mandoline or sharp knife, aiming for approximately 1/8 inch thickness.
  • In a large skillet over medium heat, melt the butter with olive oil. Add the sliced onions and sugar, then cook slowly, stirring occasionally for 15-20 minutes until they reach a deep golden brown.
  • Once onions are caramelized, add minced garlic and thyme, cooking for another minute until fragrant. Sprinkle flour over the onion mixture and stir constantly for 1-2 minutes.
  • Gradually whisk in the beef broth, ensuring no lumps form. Simmer for 2-3 minutes until slightly thickened.
  • Reduce heat to low and slowly stir in the heavy cream. Season with salt and pepper, adjusting to taste. Allow the sauce to gently simmer for 2-3 minutes, stirring occasionally until it reaches a silky consistency that coats the back of a spoon.
  • Layer half of the sliced potatoes in the prepared baking dish, slightly overlapping them like shingles. Pour half of the onion sauce over the potatoes, ensuring even coverage. Repeat with remaining potatoes and sauce.
  • Sprinkle the shredded gruyère cheese evenly over the top of the casserole. Cover the dish with aluminum foil, ensuring it doesn't touch the cheese.
  • Bake covered for 40 minutes, then remove the foil and bake for an additional 15 minutes until the cheese is bubbly and golden brown, and potatoes are fork-tender.
  • In the final 5 minutes, sprinkle the crispy fried onions on top for an extra layer of texture and flavor.
  • Allow the casserole to rest for 10 minutes before serving. Sprinkle with fresh parsley before serving.

Notes

For a lighter version, substitute the heavy cream with a mixture of 1/2 cup low-fat Greek yogurt and 1/2 cup milk.
Make-Ahead Option: Prepare the casserole up to 24 hours in advance, cover and refrigerate. Add an extra 10 minutes to the covered baking time when cooking from cold.
For best results when reheating, use a 325°F oven covered with foil for 15-20 minutes rather than microwaving.

Nutrition

Calories: 310kcalCarbohydrates: 28gProtein: 8gFat: 19gSaturated Fat: 11gCholesterol: 55mgSodium: 480mgFiber: 3gSugar: 4g
Keyword Potato Casserole, French Onion, Comfort Food, Holiday Side Dish
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