French Onion Grilled Cheese Sandwich Recipe
French onion Grilled Cheese Sandwich with caramelized onions and gruyere cheese. Serve with a salad for a delicious vegetarian dinner. Vegan adaptable.
How to Make the Best French Onion Grilled Cheese Sandwich
If you love the rich, savory flavors of French onion soup, this French Onion Grilled Cheese Sandwich is about to become your new favorite comfort food. It combines perfectly caramelized onions with melty Gruyere cheese between slices of crusty bread—all the best parts of the classic soup, but in handheld form.
The secret to this sandwich is taking the time to properly caramelize the onions. Low and slow is the key—rushing this step will leave you with soft onions instead of the deep, sweet, jammy caramelized goodness that makes this sandwich special. A splash of sherry or port adds an extra layer of complexity that takes the flavor to the next level.
Serve this grown-up grilled cheese with a simple green salad for a satisfying vegetarian dinner, or pair it with a cup of tomato soup for the ultimate comfort food experience. It’s also easily adaptable for vegan diets by using plant-based butter and vegan cheese.
French Onion Grilled Cheese Sandwich
French onion Grilled Cheese Sandwich with caramelized onions and gruyere cheese. Serve with a salad for a delicious vegetarian dinner. Vegan adaptable.
Ingredients
Caramelized Onions
Sandwich
Instructions
Caramelized Onions
- In a large heavy bottom skillet or cast iron pan, heat oil over medium heat. Add onion and sauté for 5 minutes, stirring to coat. Turn heat down to medium low. Stir occasionally and continue sautéing for 20 minutes.
- Onions will sweat out their moisture and eventually caramelize into a beautiful deep golden brown. Add a generous pinch of salt, a splash of port, sherry, or stock (optional) and let the liquid cook off. Remove from pan and wipe it out with a paper towel to use again. Preheat oven to 350°F.
Assemble and Cook
- Spread the bread with whole grain mustard (optional). On two slices, divide and layer shredded Gruyere, top with caramelized onions, sprinkle with fresh thyme leaves, then add the rest of the cheese. 'Put the lid on' the sandwiches with the other slices of bread and gently press together.
- Heat butter and olive oil in the same skillet over medium-low heat. Place sandwiches in the pan and toast, carefully flipping when perfectly golden brown and cheese begins to melt.
- Place in a warm oven to fully melt the cheese, which will prevent the bread from getting too dark. Cut in half and enjoy.
Notes
- For best results, slice onions uniformly thin for even caramelization.
- Gruyere is traditional for French onion soup flavor, but Swiss or fontina also work well.
- The caramelized onions can be made ahead and stored in the refrigerator for up to 5 days.
