French Onion Grilled Cheese Sandwich Recipe

If you’re a fan of classic French onion soup and love a good grilled cheese sandwich, then this recipe will be your new favorite comfort food. A French Onion Grilled Cheese Sandwich brings together the savory, sweet flavor of caramelized onions and the creamy richness of melted cheese, all sandwiched between crispy, buttery bread. It’s an elevated version of the traditional grilled cheese, loaded with depth and character, perfect for a cozy meal at home.

Step-by-Step Instructions

Step 1: Caramelizing the Onions

The heart of a French Onion Grilled Cheese Sandwich lies in perfectly caramelized onions. This process takes patience but rewards you with rich, sweet, and savory onions that add a deep, unforgettable flavor to your sandwich.

1. Prepare the Onions: Peel and thinly slice the onions. Aim for uniform slices, about 1/8-inch thick, to ensure they cook evenly.
2. Melt the Butter and Oil: In a large skillet, melt 2 tablespoons of unsalted butter and 1 tablespoon of olive oil over medium heat. The butter adds richness, while the olive oil prevents the butter from burning.
3. Add the Onions: Add the sliced onions to the skillet and toss them to coat evenly in the butter and oil. Sprinkle with salt, pepper, and sugar (if using). The sugar helps speed up the caramelization process, but it’s optional.
4. Cook the Onions: Cook the onions over medium-low heat, stirring every few minutes to prevent burning. This process will take about 25-30 minutes. As the onions cook, they’ll slowly turn golden brown and become tender and sweet. Adjust the heat if needed to avoid burning or sticking.
5. Deglaze the Pan: Once the onions are caramelized, deglaze the pan by adding the beef broth (or vegetable broth) and thyme. Stir to scrape up any browned bits from the bottom of the skillet. Allow the liquid to reduce until the onions are coated in a flavorful glaze, about 3-4 minutes. Remove from heat and set aside.

Step 2: Preparing the Sandwich

1. Prepping the Bread: Choose a rustic, sturdy bread that can hold up to the weight of the caramelized onions and cheese. Sourdough or French bread are ideal. Spread softened butter generously on one side of each slice of bread.
2. Assembling the Sandwich: On the unbuttered side of four slices of bread, spread a thin layer of Dijon mustard for extra tang (optional). Next, layer two slices of Gruyère cheese on each slice of bread. Top the cheese with a generous helping of caramelized onions, spreading them evenly. Add a slice of provolone cheese on top of the onions for creaminess.
3. Finishing the Sandwich: Place the remaining four slices of bread on top, buttered side out, to complete the sandwich. Press down gently to ensure all the ingredients are evenly distributed.

Step 3: Grilling the Sandwich

1. Preheat the Skillet: Heat a large skillet or griddle over medium heat. If you’re making multiple sandwiches, you may need to work in batches.
2. Grill the Sandwich: Place the assembled sandwiches in the skillet, buttered side down. Grill for about 3-4 minutes on the first side, pressing gently with a spatula to ensure even browning. The goal is to achieve a crispy, golden exterior without burning the bread.
3. Flip the Sandwich: Carefully flip the sandwich and cook for another 3-4 minutes on the other side, until the bread is golden and the cheese is fully melted. Reduce the heat if the bread is browning too quickly before the cheese has a chance to melt.
4. Optional Finish in the Oven: If you’re making multiple sandwiches or want to ensure the cheese is fully melted without overcooking the bread, you can finish the sandwiches in a preheated 350°F (175°C) oven for 5-7 minutes.

Step 4: Serving

1. Slice and Serve: Once the sandwiches are grilled to perfection, remove them from the skillet and let them cool for a minute or two. Slice the sandwiches in half diagonally for a classic presentation.
2. Garnish: For a touch of freshness, garnish the sandwiches with fresh parsley. You can also serve with a side of extra caramelized onions or a small cup of French onion soup for dipping.
3. Optional Toppings: Feel free to customize your sandwich with additional toppings like sliced tomatoes, baby spinach, or even a drizzle of hot sauce for extra heat. The sky’s the limit with this versatile recipe!

Variations and Additions

1. Add Meat:

For a heartier version, add thinly sliced roast beef, ham, or turkey between the layers of cheese and caramelized onions. This turns the sandwich into a French Onion Melt.

2. Vegetarian Option:

Skip the beef broth and use vegetable broth for the caramelized onions to make this sandwich fully vegetarian. You can also add sautéed mushrooms for extra texture and flavor.

3. Use Different Cheeses:

While Gruyère and provolone are classic choices, feel free to experiment with other cheeses. Sharp cheddar, fontina, or Havarti all melt beautifully and can add different flavor profiles to the sandwich.

4. Onion Jam:

If you’re in a hurry and don’t want to spend time caramelizing onions, you can use store-bought onion jam. While it’s not the same as freshly caramelized onions, it still adds that sweet-savory flavor you’re looking for.

5. Herbed Butter:

Elevate your grilled cheese even further by using an herbed butter to spread on the bread. Mix softened butter with garlic, thyme, and a pinch of rosemary for added depth of flavor.

Tips for Perfecting Your French Onion Grilled Cheese

1. Patience with Onions: Caramelizing onions is a slow process, but rushing it will result in burnt onions rather than the sweet, deep flavor you’re aiming for. Keep the heat low and stir frequently.
2. Choose the Right Cheese: The combination of Gruyère and provolone is ideal for a gooey, melty sandwich, but you can experiment with your favorites. Just make sure to pick cheeses that melt well.
3. Press the Sandwich: Use a spatula to press the sandwich gently while grilling. This helps create an even golden crust and ensures that the cheese melts throughout.
4. Don’t Skimp on the Butter: The buttered bread creates that golden, crispy exterior, so be generous when spreading it on the bread. For an extra indulgent touch, you can use garlic butter for added flavor.

Serving Suggestions

French Onion Grilled Cheese Sandwiches are rich and flavorful, so pairing them with lighter sides can balance the meal. Here are a few ideas:

• Side Salad: A simple green salad with a light vinaigrette can provide a refreshing contrast to the richness of the sandwich.
• French Onion Soup: Why not go all-in with the French onion theme? Serve with a small bowl of French onion soup for dipping.
• Roasted Vegetables: Roasted carrots, Brussels sprouts, or asparagus make excellent side dishes.
• Pickles: The tangy crunch of a pickle can cut through the richness of the grilled cheese.

Storage and Reheating

Storing Leftovers:

If you have leftover sandwiches, you can store them in an airtight container in the refrigerator for up to 2 days. Keep in mind that the bread will lose some of its crispiness when stored, but you can reheat it to regain some of that texture.

Reheating:

To reheat, place the sandwiches on a baking sheet and warm them in a 350°F (175°C) oven for about 10 minutes, or until heated through. This will help the bread regain its crispiness without becoming soggy.

Conclusion

The French Onion Grilled Cheese Sandwich is a decadent twist on a beloved classic, combining the best of French onion soup with the comfort of a grilled cheese sandwich. Whether you’re making it for a quick lunch or a comforting dinner, this recipe will leave you and your guests satisfied with its rich, savory flavors. Enjoy the sweet, caramelized onions, gooey cheese, and crispy bread in every bite!

Yield: 4

French Onion Grilled Cheese Sandwich Recipe

Print

If you're a fan of classic French onion soup and love a good grilled cheese sandwich, then this recipe will be your new favorite comfort food. A French Onion Grilled Cheese Sandwich brings together the savory, sweet flavor of caramelized onions and the creamy richness of melted cheese, all sandwiched between crispy, buttery bread. It’s an elevated version of the traditional grilled cheese, loaded with depth and character, perfect for a cozy meal at home.

Prep Time 10 minutes

Cook Time 30 minutes

Total Time 40 minutes

Ingredients

• For the Onion Filling:
• 2 large yellow onions, thinly sliced
• 2 tbsp butter
• 1 tbsp olive oil
• 1 tsp sugar
• 1 tsp balsamic vinegar (optional)
• 1/4 tsp salt
• 1/4 tsp black pepper
• 1/4 cup beef broth (or vegetable broth)
• For the Sandwich:
• 8 slices of sourdough bread (or your favorite bread)
• 2 cups shredded Gruyère cheese (or Swiss cheese)
• 1/2 cup shredded mozzarella cheese
• 4 tbsp butter (for grilling the sandwiches)
• Fresh thyme leaves (optional, for garnish)

Instructions

1. Caramelize the Onions:

• In a large skillet, heat the butter and olive oil over medium heat.
• Add the sliced onions, sugar, salt, and pepper. Cook for about 20 minutes, stirring occasionally, until the onions are golden brown and caramelized.
• Add the balsamic vinegar (if using) and beef broth, and cook for an additional 2-3 minutes until the liquid is absorbed and the onions are jammy. Remove from heat and set aside.

2. Assemble the Sandwiches:

• Spread a generous layer of the caramelized onions on one side of four slices of bread.
• Top with a mixture of shredded Gruyère and mozzarella cheese.
• Place the remaining slices of bread on top to form the sandwiches.

3. Grill the Sandwiches:

• Heat a large skillet or griddle over medium heat. Spread butter on the outside of each sandwich.
• Place the sandwiches in the skillet and cook for 3-4 minutes on each side, pressing down gently with a spatula, until the bread is golden and crispy, and the cheese is melted.

4. Serve:

• Once the sandwiches are golden and crispy, remove them from the skillet. Slice in half and garnish with fresh thyme leaves (optional).

Notes

Cheese Substitutions: If you can’t find Gruyère, Swiss cheese or provolone are great alternatives.

Extra Flavor: For a stronger French onion flavor, sprinkle a little beef broth concentrate or bouillon powder into the caramelized onions before assembling the sandwiches.

Storage: These sandwiches are best served fresh, but you can refrigerate any leftover caramelized onions for up to 5 days to make more sandwiches later.