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.
Ingredients
- For the Caramelized Onions: 2 tablespoons unsalted butter, 2 large yellow onions, thinly sliced, 1 teaspoon sugar, 1/2 teaspoon salt, 1/4 teaspoon freshly ground black pepper, 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried), 1 tablespoon balsamic vinegar
- For the Sandwich: 4 slices sourdough or country style bread, 2 tablespoons unsalted butter softened, 1 cup (about 100 g) shredded Gruyère cheese, 1 cup (about 100 g) shredded mozzarella cheese, 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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Pin It Recipe Questions & Answers
- → How do I caramelize onions properly?
Cook sliced onions over medium heat with butter, sugar, salt, and pepper, stirring occasionally for 25–30 minutes until golden brown and deeply caramelized.
- → What cheeses work best for this sandwich?
Gruyère and mozzarella create a creamy, flavorful melt. You can also swap Gruyère with Comté or Swiss cheese for variations.
- → Can I use a different type of bread?
Sourdough or country-style bread is recommended for its texture and flavor, but any sturdy bread with a good crust works well.
- → How do I achieve a crispy crust on the sandwich?
Butter the outside of the bread slices and cook on medium-low heat, pressing gently and flipping once, until golden and crisp.
- → Can I prepare the onions ahead of time?
Yes, caramelized onions can be made in advance and stored refrigerated for up to 3 days, making assembly quicker.