French Onion Grilled Cheese

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.

Ingredients

• For the Caramelized Onions: 2 tablespoons unsalted butter
• For the Caramelized Onions: 2 large yellow onions, thinly sliced
• For the Caramelized Onions: 1 teaspoon sugar
• For the Caramelized Onions: 1/2 teaspoon salt
• For the Caramelized Onions: 1/4 teaspoon freshly ground black pepper
• For the Caramelized Onions: 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried)
• For the Caramelized Onions: 1 tablespoon balsamic vinegar
• For the Sandwich: 4 slices sourdough or country style bread
• For the Sandwich: 2 tablespoons unsalted butter, softened
• For the Sandwich: 1 cup (about 100 g) shredded Gruyère cheese
• For the Sandwich: 1 cup (about 100 g) shredded mozzarella cheese
• For the Sandwich: 2 teaspoons Dijon mustard

Instructions

Step 1:

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 25–30 minutes.

Step 2:

Stir in thyme and balsamic vinegar cook another 2 minutes until fragrant. Remove from heat and set aside.

Step 3:

Butter one side of each bread slice. Spread Dijon mustard on the unbuttered side of two slices.

Step 4:

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.

Step 5:

Heat a clean skillet or griddle over medium low heat. Cook sandwiches 3–5 minutes per side, pressing gently and flipping once, until bread is golden and cheese is fully melted.

Step 6:

Let rest 1 minute before slicing. Serve hot.

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Pairs beautifully with tomato soup or a simple green salad.