French Onion Soup Grilled Cheese Sandwiches

Ingredients

• 4 tablespoonsunsalted butter
• 2 largeyellow onions, sliced 6 mm thick
• 2 clovesgarlic, finely minced
• 1 teaspoonfresh thyme leaves
• ¾ teaspoonkosher salt
• ½ teaspoonblack pepper
• 3 tablespoonsdry white wine (or beef stock or beer)
• 8 slicessourdough bread
• 227 g (8 oz)Gruyère cheese, grated
• 4 tablespoonssalted butter

Instructions

1. 1

   Melt the butter

   Melt 4 tablespoons of unsalted butter in a large pan over medium-high heat.

2. 2

   Slice the onions

   Meanwhile, trim the tops and bottoms from the onions and slice them 6 mm (¼ inch) thick. Keeping the slices even helps them cook at the same rate.

3. 3

   Coat the onions

   Once the butter has melted, add the onions, garlic, thyme, kosher salt and pepper. Toss to coat, cover the pan and cook without stirring for 5 minutes.

4. 4

   Cook until golden

   Uncover the pan, reduce the heat to medium-low and cook for 40 minutes, stirring every 5 minutes, until the onions are soft and deep golden in colour.

5. 5

   Deglaze with wine

   Pour in the wine and scrape up any bits stuck to the bottom of the pan. Remove the pan from the heat.

6. 6

   Build the sandwiches

   Top four slices of sourdough with grated Gruyère, the caramelised onions and more Gruyère. Put the remaining bread slices on top.

7. 7

   Heat the griddle

   Preheat a griddle to 150°C (300°F). Melt 1 tablespoon of salted butter per sandwich, spreading it into pools about the size of the sandwiches.

8. 8

   Start grilling

   Set the sandwiches gently on the griddle and press them into the butter. Adjust the griddle's heat if needed as they cook.

9. 9

   Brown the first side

   Griddle the sandwiches until the undersides are crisp and deep golden brown.

10. 10

    Flip the sandwiches

    Before flipping, lift each sandwich with a spatula. Melt another tablespoon of butter per sandwich on the griddle, as before, then carefully turn the sandwiches over and gently press them into the butter.

11. 11

    Finish and serve

    Once the cheese has melted and the second sides are crisp and golden, transfer the sandwiches to a cutting board. Cut them in half and serve.

What are French onion soup grilled cheese sandwiches?

This American-style sandwich takes inspiration from French onion soup, pairing slowly browned onions with Gruyère and toasted bread. The soup itself is a French classic; here, its familiar onion-and-cheese combination is tucked between slices of sourdough.

The recipe works because the onions cook until soft and deeply golden before being finished with wine, garlic and thyme. Gruyère melts around the savoury filling, while the buttered bread gives each sandwich a crisp exterior.

Nutrition and macros by portion

The nutrition label shows one serving as written: 847 calories, 33g protein, 81g carbs, 43g fat.

The sourdough supplies most of the carbohydrates, while the butter and Gruyère contribute much of the fat. Gruyère also provides most of the protein. Pair a sandwich with a green salad or extra vegetables to balance the plate.

The onion filling

Even slices: Cut the onions to a consistent 6 mm thickness so they soften at a similar pace. Keep the heat moderate after the initial covered cooking to help them turn golden without scorching.

Wine: Pour it in after the onions are cooked, then scrape the pan to lift the browned bits. Beef stock or beer can be used instead, as noted in the ingredient list.

Choosing the bread and cheese

Sourdough: Its sturdy slices hold the onion filling and stand up to the buttered griddle. If the slices vary in size, pair similar ones together so the sandwiches brown evenly.

Gruyère: Grate the cheese so it melts readily between the bread. Layering it on both sides of the onions helps hold the filling together as the sandwiches are flipped.

Getting the griddle right

Steady heat: The method specifies 150°C, a moderate griddle temperature for crisping the bread while the cheese melts. Adjust the heat during cooking if the bread is browning too quickly or too slowly.

Butter coverage: Spread the butter into pools about the size of each sandwich, then set the bread down gently. The second side gets fresh butter too, so take care when flipping the sandwiches.

How to tell when they are ready

Onions: Look for soft slices with a deep golden colour, stirring every 5 minutes during the 40-minute uncovered cook. Pale or firm onions need more time.

Sandwiches: The outside should be crisp and deep golden, and the cheese should be melted before serving. Transfer them to a board before cutting in half.

Timing and serving

The supplied total time is 5 minutes, but the written method includes 5 minutes of covered onion cooking and 40 minutes uncovered, followed by sandwich assembly and griddling. Allow substantially longer than 5 minutes to make the recipe as written.

Serve the sandwiches hot, while the cheese is melted and the bread is crisp. A simple green salad or a bowl of vegetable soup makes a fresh, practical accompaniment.

Recipe notes & tips

• Slice the onions evenly so they cook at a similar rate.
• Stir the onions every 5 minutes during their uncovered cooking time.
• Grate the Gruyère before assembling the sandwiches.
• Keep the griddle at a moderate heat and adjust it if the bread browns too quickly.
• Use a spatula to support each sandwich when flipping it.
• Let the sandwiches sit briefly on the cutting board before slicing.

Variations

• Use beef stock: Swap it for the white wine to keep the onion filling savoury without wine.
• Try beer: Use beer instead of wine for a deeper, malty note.
• Change the cheese: Use another good-melting cheese if Gruyère is unavailable.
• Add extra thyme: Increase the fresh thyme for a more pronounced herbal flavour.
• Serve with salad: Add a crisp green salad alongside the sandwich for freshness.

Common mistakes to avoid

• Uneven onion slices: Cut them to a consistent thickness so some do not stay firm while others soften.
• High heat for too long: Reduce to medium-low after the covered 5-minute cook to help the onions brown without burning.
• Skipping the pan scrape: Scrape the browned bits into the wine for more flavour in the filling.
• Overfilling the bread: Spread the onions evenly and keep the filling within the slices to make flipping easier.
• Griddle too hot: Lower the heat if the bread darkens before the cheese melts.
• Flipping without support: Lift the sandwich carefully with a spatula to keep the filling in place.

How to store

These sandwiches are best eaten hot and fresh. Refrigerate leftovers in an airtight container for up to 3 days, then reheat in a pan or on a griddle over medium-low heat until hot and crisp again.

Frequently asked questions