Caramelized Onion Grilled Cheese
Caramelized Onion Grilled Cheese Sandwiches turn a simple sandwich into something that feels a little extra, with little work. The onions bring a rich, slightly sweet layer that melts right into the cheese, and the bread gets crisp and golden on the outside.
The best part is that these come together fast when you already have caramelized onions tucked away in the freezer.
🍽️ Recipe Name: Caramelized Onion Grilled Cheese
⏰ Ready In: 10 minutes
⏳ Prep Time: 2 minutes
🔥 Cook Time: 8 minutes
👥 Serves: 8 sandwiches
🥕Main Ingredients: Bread, caramelized onions, cheese, mayonnaise or butter
🍳 Special Equipment: Skillet or air fryer, spatula
⭐ Why You’ll Love It: Crispy, cheesy, and a great way to turn leftover caramelized onions into an easy meal
What You Need
- Caramelized Onions: You can make a large batch of caramelized onions and freeze them in single-serving packages for easy meal prep.
- Bread: Choose your favorite bread. Whole wheat, white and rye are all delicious.
- Mayonnaise: Mayonnaise or melted butter to baste the bread. Mayonnaise actually makes a crispier crust.
- Cheese: A good melting cheese and a flavorful cheese are the best combination.
For the Onions
- Onions: Use any onion you have on hand. Yellow onions are the most commonly used.
- Olive oil: Just a little to coat the pan.
- Butter: Butter adds a rich flavor.
- Molasses: The secret to the best caramelized onions. It adds a bold, dark or light brown sugar flavor, yet produces a silkier dish than using brown sugar.
- Salt and Pepper: Season the onions.
How to Make Them
Slice the onions into even thicknesses. Add unsalted butter and olive oil to a cast-iron skillet.
Season with salt and black pepper. Cook on low heat.
Once the onions soften, pour molasses on them and stir them up. They take time, but the flavor makes it worth it. For the complete recipe for caramelized onions, see our tutorial.
Spread the mayonnaise on both sides of the bread. Toast one side in a skillet over medium heat until golden brown.
Flip the bread. Build the sandwich on the toasted side of the bread. Add the cheese and top with the onions. Place the toasted side of the second slice of bread on top of the caramelized onions.
Fry until the bottom piece of toast is a deep golden brown. Carefully flip the sandwich over. Toast the second side. Place a bowl or lid over the sandwich to help melt the cheese. Pro Tip: When you hear the bread stop sizzling, it’s perfectly toasted.
How to Cook Them in the Air Fryer
Spread mayonnaise on one side of each piece of bread.
Repeat with the remaining slices of bread.
Place one slice of bread mayonnaise side down in the air fryer basket. Add cheese on the dry side of the bread.
Top with caramelized onions and the second piece of bread, with the dry side down.
Air-fry for 4-5 minutes, until golden brown. Flip. Air fry an additional 4-5 minutes.
Cheese should be melty and bread golden. Serve hot.
Types of Cheese to Use
We like using one cheese for flavor and one that melts well, so the sandwich gets both a rich taste and that soft, stretchy center.
- Cheddar cheese
- Swiss
- American
- Gouda
- Fontina
Types of Bread to Use
Almost any sandwich bread works here, but sturdier slices hold up best once the onions and cheese melt together.
- White
- Wheat
- Sourdough
- Rye
More Caramelized Onion Recipes
More Sandwiches
- Apple Grilled Cheese
- Ham and Cheese Grilled Cheese
- Air Fryer Grilled Cheese
- Tuna Melt
- Spicy Fish Sandwich
- Spicy Grilled Cheese
- Reuben Sandwich
Helpful Tools
Use Swiss cheese, and these sandwiches taste like French onion soup in sandwich form.
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I hope you enjoyed the recipe today.
Enjoy. And have fun cooking!
Caramelized Onion Grilled Cheese
Ingredients
For the Caramelized Onions
- 1 medium onion
- ¼ cup molasses
- 2 tablespoons butter
- 1 tablespoon olive oil
- 1 teaspoon salt
- ½ teaspoon cracked black pepper
- 2 tablespoons balsamic or red-wine vinegar
For the Sandwiches
- 16 slices bread
- 16 slices cheese
- 8 tablespoons mayonnaise
Instructions
For the Onions
- Slice the onions into uniform thickness slices. You can choose very thin or medium, which is about ¼-inch.
- Add the butter and oil to a skillet. Top with the onions and season them with the salt and pepper.
- Cook on medium-low, stirring often until the onions soften. Pour in the molasses.
- Continue cooking and stirring every few minutes until the onions are very soft and a deep golden brown.
- Deglaze the skillet with vinegar, water or beef broth and scrape the browned bits from the bottom. Let the liquid cook off completely. Cool.
For the Grilled Cheese
- Spread mayo on both sides of the bread. Toast one side in the skillet. Flip and build the sandwiches in the pan.
- Layer the cheese on the toasted side of one piece of bread. Top with a couple of tablespoons of caramelized onions. Top with another piece of bread, toasted side down.
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