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French Onion Grilled Cheese Sandwich with Caramelized onions, melty Gruyere and toasty bread. A cozy vegetarian dinner perfect for the colder months! #grilledcheese #sandwich #frenchonion #grilledcheesesandwich #vegetarianrecipes

French Onion Grilled Cheese Sandwich

5 Stars 4 Stars 3 Stars 2 Stars 1 Star 5 from 13 reviews
  • Author: Sylvia Fountaine | Feasting at Home Blog
  • Prep Time: 15 mins
  • Cook Time: 45 mins
  • Total Time: 50 mins
  • Yield: 2 1x
  • Category: Sandwich, vegetarian
  • Method: Stovepot
  • Cuisine: Northwest, vegetarian
  • Diet: Vegetarian


French onion Grilled Cheese Sandwich with caramelized onions and gruyere cheese. Serve with a salad for a delicious vegetarian dinner. Vegan adaptable.


Units Scale
  • 1 large red, sweet or yellow onion- thinly sliced about 1/8 in thick
  • 12 tablespoons olive oil
  • generous pinch salt
  • pinch fresh cracked pepper
  • 1 tsp fresh thyme (optional)
  • 1/4 cup sherry cooking wine, port, or beef stock (all optional, or sub a splash of balsamic vinegar)
  • 4 slices hearty bread or French Bread
  • 1 tablespoons butter ( or sub olive oil)
  • 1 tablespoon olive oil
  • 1 cup grated or sliced Gruyere cheese ( or meltable vegan cheese)
  • Whole grain Mustard ( optional)


  1. In a large heavy bottom skillet, or cast iron pan, heat oil over medium heat. Add onion and saute for 5 minutes, stirring to coat. Turn heat down to medium low. Stir occasionally and continue sauteing for 20 minutes.
  2. Onions will sweat out their moisture, and eventually caramelize into a beautiful deep golden brown. Add a generous pinch of salt, a splash of port, sherry, or stock (optional) and let the liquid cook off. Remove from pan and wipe it out with a paper towel, to use again.  Preheat oven to 350 F
  3. Spread the bread with whole grain mustard (optional). On two slices, divide and layer shredded Gruyere, top with caramelized onions, sprinkle with fresh thyme leaves, then add the rest of the cheese. “Put the lid on” the sandwiches with the other slices of bread and gently press together
  4. Heat butter and olive oil in the same skillet over medium-low heat. Place sandwiches in the pan and toast, carefully flipping when perfectly golden brown and cheese begins to melt.
  5. Place in a warm oven to fully melt the cheese -which will preventing the bread from getting too dark. Cut in half and enjoy.


  • Serving Size: ½ sandwich
  • Calories: 520
  • Sugar: 4.9 g
  • Sodium: 1049.1 mg
  • Fat: 22.5 g
  • Saturated Fat: 9.5 g
  • Carbohydrates: 58.5 g
  • Fiber: 3.5 g
  • Protein: 21.8 g
  • Cholesterol: 43.9 mg