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.
This sandwich quickly became a favorite in my household for its perfect balance of sweet onions and melted cheese comfort.
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Ingredients
- 2 tablespoons unsalted butter: for caramelizing onions and spreading on bread
- 2 large yellow onions, thinly sliced: the base of the caramelized onions
- 1 teaspoon sugar: enhances onion sweetness
- 1/2 teaspoon salt: seasoning for onions
- 1/4 teaspoon freshly ground black pepper: adds subtle spice
- 1 teaspoon fresh thyme leaves (or 1/2 teaspoon dried): herbs for flavor
- 1 tablespoon balsamic vinegar: adds depth
- 4 slices sourdough or country-style bread: sandwich base
- 2 tablespoons unsalted butter, softened: for spreading on bread
- 1 cup shredded Gruyère cheese: melty, savory cheese
- 1 cup shredded mozzarella cheese: adds creaminess
- 2 teaspoons Dijon mustard: tangy spread
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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 My family loves enjoying these sandwiches together on cozy weekend afternoons.
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Required Tools
Large skillet, spatula, bread knife, cheese grater
Allergen Information
Contains Milk (cheese, butter), Wheat (bread), Mustard. Check store-bought bread for additional allergens.
Nutritional Information
Per serving: Calories 540, Total Fat 32 g, Carbohydrates 44 g, Protein 22 g.
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This sandwich is perfect comfort food elevated with simple ingredients and care.
Recipe FAQ
- → How do I caramelize onions properly?
Cook thinly sliced onions slowly in butter with sugar and salt over medium heat, stirring occasionally until they turn a deep golden brown and develop a sweet, rich flavor, usually about 25–30 minutes.
- → Which cheeses work best for melting?
Gruyère and mozzarella are excellent choices as they melt smoothly, combining creaminess with rich, nutty and mild flavors that complement the onions.
- → Can I use other breads besides sourdough?
Yes, country-style or similar sturdy breads work well, as they hold up during grilling and develop a crisp exterior while keeping the inside soft.
- → What does the Dijon mustard add?
The mustard adds a subtle tangy and slightly sharp note that enhances the overall flavor balance without overpowering the sandwich.
- → How do I get a perfectly grilled crust?
Butter the bread slices well and cook the sandwich over medium-low heat, pressing gently and flipping once, until golden brown and the cheese is melted, about 3-5 minutes per side.
