French Onion Grilled Cheese

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French Onion Grilled Cheese

This French Onion Grilled Cheese levels up your grilled cheese game with sweet and savory caramelized onions and gooey, melty cheese all tucked between crispy, golden slices of bread. This sandwich is comfort food at its finest - perfect for lunch, dinner or a cozy snack!

Course Main Dish

Cuisine American

Keyword french onion grilled cheese, french onion soup grilled cheese, french onion soup grilled cheese sandwich

Prep Time 15

Cook Time 30

Servings

Calories 822kcal

Author Trish - Mom On Timeout

Ingredients

2 tablespoons salted butter
1 tablespoon extra virgin olive oil or salted butter
2 large white onions thinly sliced
2 large yellow onions thinly sliced
2 tablespoons Worcestershire sauce
2 teaspoons spicy brown mustard
1 teaspoon Italian seasoning
½ teaspoon garlic powder
1 teaspoon granulated sugar helps with the caramelization, optional
½ teaspoon fresh ground black pepper
½ teaspoon fine sea salt
6 slices bread French, sourdough, brioche, etc.
3 tablespoons mayonnaise optional, for spreading onto the bread
6 slices Provolone cheese
6 slices Gruyere cheese

Instructions

Heat butter and extra virgin olive oil in a large skillet over medium heat.
2 tablespoons salted butter, 1 tablespoon extra virgin olive oil
Add the sliced onions, Worcestershire sauce, spicy brown mustard, Italian seasoning, garlic powder, sugar (if using), black pepper and salt. Stir to combine.
2 large white onions, 2 large yellow onions, 2 tablespoons Worcestershire sauce, 2 teaspoons spicy brown mustard, 1 teaspoon Italian seasoning, ½ teaspoon garlic powder, 1 teaspoon granulated sugar, ½ teaspoon fine sea salt, ½ teaspoon fresh ground black pepper
Cook, stirring occasionally, until the onions are golden brown and caramelized (about 20–25 minutes). Cook until the liquid evaporates. Set aside.
Heat a clean skillet over medium heat.
Spread mayonnaise on one side of each bread slice (optional, for extra crispiness).
6 slices bread, 3 tablespoons mayonnaise
Place bread in skillet, mayonnaise side down.
Top with slices of Provolone, followed by the caramelized onions and finish with Gruyère.
6 slices Provolone cheese, 6 slices Gruyere cheese
Top with another slice of bread (mayo side facing out).
Cook until the bread is golden brown and crispy, and the cheese is melted, about 2-3 minutes per side.
Slice in half and serve immediately with your favorite chips.

Notes

Storage and Make-Ahead Information

This sandwich is best made and served immediately. That being said, here are some options for making ahead and storing leftovers:

Make Ahead: Caramelized onions can be prepared up to 3 days in advance and stored in the refrigerator.
Freezing: Assemble the sandwiches without grilling, wrap them tightly, and freeze for up to 2 months. Thaw before grilling.
Reheating: Warm leftovers in a skillet or oven to retain crispness.

Caramelizing onions takes time so do not rush the process by turning up the heat. Low and slow cooking ensures the natural sugars develop their deep, sweet flavor.

Please see post above for more information, recipe tips and frequently asked questions.

Nutrition