Pin It A decadent twist on classic grilled cheese, this sandwich combines caramelized onions with gooey melted cheese for a deeply savory, next-level comfort food experience.
I remember the first time I made this sandwich; the house filled with intoxicating aromas as the onions caramelized to perfection. It quickly became a favorite comfort meal in our family.
Ingredients
- Unsalted butter: 2 tablespoons for onions, 2 tablespoons softened for sandwich
- Yellow onions: 2 large, thinly sliced
- Sugar: 1 teaspoon
- Salt: 1/2 teaspoon
- Freshly ground black pepper: 1/4 teaspoon
- Fresh thyme leaves (or dried): 1 teaspoon fresh or 1/2 teaspoon dried
- Balsamic vinegar: 1 tablespoon
- Bread: 4 slices sourdough or country-style
- Gruyère cheese: 1 cup about 100 g shredded
- Mozzarella cheese: 1 cup about 100 g shredded
- Dijon mustard: 2 teaspoons
Instructions
- Caramelize onions:
- Melt 2 tablespoons butter in a large skillet over medium heat Add sliced onions, sugar, salt, and pepper Cook, stirring occasionally, until onions are golden brown and deeply caramelized, about 25 to 30 minutes
- Add flavorings:
- Stir in thyme and balsamic vinegar cook another 2 minutes until fragrant Remove from heat and set aside
- Prepare bread:
- Butter one side of each bread slice Spread Dijon mustard on the unbuttered side of two slices
- Assemble sandwich:
- Layer half the Gruyère and mozzarella onto the mustard side Top with a generous spoonful of caramelized onions, then the remaining cheese Place the other bread slices on top, buttered side facing out
- Cook sandwiches:
- Heat a clean skillet or griddle over medium-low heat Cook sandwiches 3 to 5 minutes per side, pressing gently and flipping once, until bread is golden and cheese is fully melted
- Serve:
- Let rest 1 minute before slicing Serve hot
Pin It Making this sandwich always brings back fond memories of sharing meals and laughter with my family around the table.
Serving Suggestions
Pairs beautifully with tomato soup or a simple green salad to balance the richness of the sandwich.
Variations
Swap Gruyère for Comté or Swiss cheese or add a sprinkle of grated Parmesan before serving for extra flavor.
Allergen Information
Contains milk (cheese, butter), wheat (bread), and mustard Check for additional allergens if using store-bought bread.
Pin It Enjoy this deeply satisfying French onion grilled cheese as a cozy meal any time you crave comfort food.
Recipe FAQs
- → How are the onions prepared?
Onions are thinly sliced and slowly cooked in butter with sugar, salt, pepper, thyme, and balsamic vinegar until deeply caramelized, enhancing their natural sweetness and flavor.
- → What cheeses are used in the sandwich?
A combination of shredded Gruyère and mozzarella cheeses provides a pleasing balance of nutty and creamy textures that melt beautifully.
- → What type of bread works best?
Sourdough or country-style bread is recommended for its sturdy texture and slight tang, perfect for holding the fillings without becoming soggy.
- → Can the cheese be substituted?
Gruyère can be swapped with Comté or Swiss cheese for similar melting properties and flavor profiles.
- → How should the sandwich be cooked?
Cook the sandwich in a skillet over medium-low heat for 3–5 minutes per side, pressing gently to achieve golden crust and full cheese melt.
- → Are there any serving suggestions?
Pair with tomato soup or a fresh green salad for a balanced meal, and optionally add grated Parmesan on top before serving.