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French Onion Soup with Mushroom Grilled Cheese is a comforting meal, perfect for a chilly night. It can be customized easily to leave everyone in the family happy.

French Onion Soup with Mushroom Grilled Cheese

The soup and sandwich combo of your dreams! The flavors in our Mushroom Grilled Cheese and French Onion Soup make a magical combination. Your taste buds will SWOON! Enjoy this soup and sandwich pairing for a comforting lunch meal, weekday supper, or even a casual Sunday Supper with the family gathered around the table.
Course Main Course
Cuisine French
Keyword Soup and Grilled Cheese
Prep Time 10 minutes
Cook Time 1 hour 15 minutes
Total Time 1 hour 25 minutes
Servings 8
Calories 826kcal


  • 2 loaf bread artisan
  • 1 pound Fontina cheese

For the soup

  • 4 large yellow onions about 3 pounds
  • ¼ cup olive oil
  • 4 sprigs thyme
  • 2 bay leaves
  • 8 cups beef broth
  • ½ teaspoon black pepper to taste
  • 2 teaspoon kosher salt to taste

For the grilled cheese

  • 8 ounce button mushroom sliced
  • 1 tablespoon olive oil
  • 1 sprig thyme
  • Salt and pepper to taste
  • 4 teaspoons salted butter softened



  • Remove the onion ends, slice in half length wise, and cut into ¼” thick slices.
  • Add olive oil to a large pot and heat over high heat.
  • Add onion, thyme and bay leaves and sauté on high heat until onion is translucent and soften, about 5 minutes.
  • Season with a few pinches of salt.
  • Reduce heat to medium high and continue to cook the onion until soft and caramelized, stirring frequently.
  • As the onion gets closer to being caramelized, the bottom of the pan may start to burn, add a little bit of the beef broth to deglaze it as the onion continues to cook.
  • When the onion is a deep golden caramel color, about 25 minutes, add the rest of the beef broth to the pot.
  • Bring to a boil and simmer for another 10 minutes, season with salt and pepper to taste.
  • Shred or grate the cheese, slice to bread into ¼” - ½” round slices that will fit the mouth of a ramekin or oven safe soup crock.
  • Remove thyme and bay leaves from the soup, and divide into your container of choice. I used ramekins (see photo above)
  • When ready to eat, place a slice of bread on top of your soup and top generously with grated Fontina cheese.
  • Broil for 4 minutes until cheese is melted and golden. (See photo above)
  • Remove from oven and serve immediately.


  • Slice the block of cheese into thin slices or use sliced deli cheese.
  • Remove thyme leaves from the sprig.
  • Heat oil in a skillet over medium high heat.
  • Add mushroom and thyme to the skillet and cook until mushroom is softened but not mushy.
  • Season with salt and pepper to taste and remove from heat.
  • Slice the loaf of bread into ⅜” - ½” thick slices.
  • Spread ½ teaspoon of butter on one side of a slice of bread.
  • Place the butter side down on the cutting board and place sliced cheese on top to cover the slice of bread.
  • Spread a quarter of the cook mushroom on top of the cheese.
  • Add more cheese on top of the mushroom.
  • Spread ½ teaspoon of butter on one side of a second slice of bread and placed the unbuttered side on top of the loaded slice.
  • Place a skillet over medium heat, and use a spatula to transfer the prepared sandwich to the hot skillet.
  • Fry until the bottom of the sandwich is golden brown.
  • Carefully flip the sandwich and cook the other side until golden brown and the cheese melted.
  • Remove from heat and repeat with the rest of the ingredients.


Calories: 826kcal | Carbohydrates: 93g | Protein: 36g | Fat: 34g | Saturated Fat: 15g | Cholesterol: 71mg | Sodium: 2832mg | Potassium: 674mg | Fiber: 8g | Sugar: 14g | Vitamin A: 605IU | Vitamin C: 7.5mg | Calcium: 580mg | Iron: 6.9mg