Save to Pinterest 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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Save to Pinterest Common Questions
- → How do you caramelize onions perfectly?
Cook sliced onions slowly over medium heat with butter, a pinch of sugar, salt, and pepper, stirring occasionally until golden and deeply browned, about 25-30 minutes.
- → Which cheeses work best for this sandwich?
Gruyère and mozzarella provide a balance of flavor and meltability, but Comté or Swiss can be used as alternatives.
- → Can I prepare the onions ahead of time?
Yes, caramelized onions can be made in advance and stored refrigerated for up to 3 days, enhancing flavors when reheated.
- → What bread types complement this sandwich?
Sourdough or country-style bread with a sturdy crumb works best to hold the filling and achieve a crisp crust.
- → How can I add extra flavor to the onions?
Adding a splash of dry white wine during cooking or a sprinkle of fresh thyme elevates the savory profile.