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Golden, crispy French Onion Grilled Cheese with rich caramelized onions and melted cheese, stacked on a black plate with chips.
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French Onion Grilled Cheese

Melty. Savory. Irresistible. This French Onion Grilled Cheese takes everything you love about the classic soup, caramelized onions, thyme, and gooey cheese, and tucks it between two slices of buttery, golden bread. It’s comfort food, leveled up.
Prep Time10 minutes
Cook Time25 minutes
Total Time35 minutes
Course: Lunch
Cuisine: American, French
Keyword: french onion grilled cheese, grilled cheese
Servings: 2
Calories: 907kcal
Author: Joanna Cismaru

Ingredients

  • 2 tablespoons butter divided
  • 1 tablespoon olive oil
  • 1 large onion thinly sliced
  • ½ teaspoon salt
  • ½ teaspoon black pepper
  • ½ teaspoon sugar
  • ½ teaspoon fresh thyme leaves or ¼ teaspoon dried
  • 2 tablespoons beef broth low sodium or water
  • 4 slices sourdough bread
  • 1 cup Gruyère cheese shredded, or Swiss
  • ½ cup mozzarella cheese shredded
  • 1 teaspoon Dijon mustard optional, for extra depth
  • 1 clove garlic halved, for rubbing the bread
US Customary - Metric

Instructions

  • Melt 1 tablespoon butter with olive oil in a skillet over medium-low heat. Add the onions, salt, pepper, sugar, and thyme. Cook, stirring occasionally, for 15–20 minutes until golden and soft. Add the beef broth and stir to deglaze the pan, cooking until absorbed. Remove from heat.
  • Butter one side of each bread slice. On the unbuttered side, spread Dijon mustard (if using), then layer half the shredded cheeses and the caramelized onions. Top with the remaining cheese and a slice of bread, buttered side facing out.
    process shots showing how to make fench onion grilled cheese.
  • Heat a clean skillet over medium-low heat. Cook each sandwich for about 3–4 minutes per side, pressing slightly with a spatula, until golden brown and the cheese is melted.
    process shots showing how to make fench onion grilled cheese.
  • Rub the toasted bread lightly with the cut side of the garlic clove for extra flavor. Slice in half and serve immediately!
    process shots showing how to make fench onion grilled cheese.

Notes

  1. Low and slow. Caramelize those onions gently, rushing them means losing that deep, sweet flavor.
  2. Gruyère is king. Swiss works too, but Gruyère brings that nutty, luxurious flavor that makes this sandwich unforgettable.
  3. Rubbing with garlic = magic. It’s a tiny step that adds big flavor, so don’t skip it.
  4. Cheese layering matters. Put cheese on both sides of the onions so it melts evenly and holds the sandwich together.
  5. Serve immediately. Like all grilled cheese, this is best piping hot and fresh off the pan.

Nutrition

Serving: 1serving | Calories: 907kcal | Carbohydrates: 76g | Protein: 41g | Fat: 49g | Saturated Fat: 25g | Polyunsaturated Fat: 4g | Monounsaturated Fat: 17g | Trans Fat: 0.5g | Cholesterol: 125mg | Sodium: 2147mg | Potassium: 387mg | Fiber: 4g | Sugar: 11g | Vitamin A: 1195IU | Vitamin C: 7mg | Calcium: 904mg | Iron: 6mg
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