Save 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.
Save Required Tools
Large skillet, Spatula, Bread knife, Cheese grater
Allergen Information
Contains: Milk (cheese, butter), Wheat (bread), Mustard. If using store-bought bread, check for additional allergens.
Nutritional Information (per serving)
Calories: 540, Total Fat: 32 g, Carbohydrates: 44 g, Protein: 22 g
Save Recipe Guide
- → How do I caramelize onions perfectly?
Sauté thinly sliced onions slowly over medium heat with butter, sugar, salt, and pepper, stirring occasionally until deep golden brown, about 25-30 minutes. Adding thyme and balsamic vinegar enhances flavor.
- → What bread works best for this sandwich?
Choose sturdy breads like sourdough or country-style that hold up to melting cheese and butter without becoming soggy.
- → Can I substitute the cheeses used?
Gruyère and mozzarella provide creaminess and flavor, but Comté or Swiss can be swapped in for a similar effect.
- → How should I cook the sandwich for best texture?
Cook over medium-low heat on a skillet or griddle, pressing gently and flipping once until bread is golden brown and cheese has fully melted.
- → What can I serve alongside this sandwich?
Pair with tomato soup, green salad, or a glass of dry white wine to complement the rich, savory flavors.