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Rustic Skillet French Onion Soup

A rich and savory caramelized onion soup cooked entirely in a cast iron skillet, topped with crusty toasted baguette and melted Gruyère cheese.
Print Recipe
Prep Time 20 minutes
Cook Time 50 minutes
Total Time 1 hour 10 minutes
Servings: 4 servings
Course: Appetizer, Dinner, Soup
Cuisine: French, Rustic
Calories: 580
Ingredients Equipment Method Notes

Ingredients
  

Soup Base
  • 5 large yellow onions thinly sliced
  • 4 tbsp unsalted butter
  • 2 tbsp olive oil
  • 3 cloves garlic minced
  • 2 tbsp all-purpose flour
  • 0.5 cup dry white wine or sherry
  • 6 cups beef broth high quality
  • 1 tsp fresh thyme leaves
  • 1 bay leaf
Topping
  • 1 French baguette sliced 1-inch thick
  • 2 cups Gruyère cheese grated
  • 0.25 cup Parmesan cheese grated (optional)

Equipment

  • Cast Iron Skillet (10-12 inch)
  • Sharp knife
  • Cutting board
  • Wooden Spoon

Method
 

  1. Heat butter and oil in a large cast iron skillet over medium heat.
  2. Add sliced onions and cook slowly, stirring often, for 45-50 minutes until caramelized and dark brown.
  3. Add minced garlic and thyme, cooking for 1 minute until fragrant.
  4. Sprinkle flour over onions, stir for 2 minutes, then deglaze with wine, scraping up browned bits.
  5. Pour in beef broth and add bay leaf. Simmer on low for 20 minutes. Season with salt and pepper.
  6. Preheat oven broiler. Toast baguette slices separately until golden.
  7. Arrange toasted bread on top of the soup in the skillet.
  8. Cover bread and soup generously with Gruyère and Parmesan cheese.
  9. Broil for 3-5 minutes until cheese is bubbly and golden brown. Serve immediately.

Notes

Patience is key for the onions; do not rush the caramelization process or the soup will lack depth. Use vegetarian broth for a meat-free version.