The Pantry
American

French onion grilled cheese

A rich grilled cheese for 2 made with deeply caramelized onions, Gruyere, provolone, and sturdy bread, finished in a skillet until the crust is crisp and the cheese is fully melted. The onions are cooked low and slow, then loosened with beef broth and a little balsamic for the savory French onion flavor.

Prep 15 minCook 35 minRest 5 minAdjust servings ↓
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French onion grilled cheese
~730 calper person · ~1460 total
~$8.25meal total · ~$4.13 per person

Estimated calories and US ingredient costs.

For 4 sandwiches, use a large skillet or griddle and cook in batches so the bread can brown evenly without steaming. Do not scale the heat upward to cook faster; keep the onions low and slow, and extend the grilling in small increments if the bread is browning faster than the cheese melts. Cheese melt and browning are approximate, so use visual doneness cues rather than exact timing when scaling.

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Ingredients, steps and a live timeline. Ready for 2 people.

Step timeline

Cooking order

9 left
Step 1

Caramelize the onions

~22 min

Caramelize the onions.

Heat 1 tbsp olive oil in a 10-inch skillet over medium-low heat.

Add 12 oz thinly sliced yellow onions, 1/2 tsp kosher salt, 1/4 tsp black pepper, and 1 tsp granulated sugar.

Cook, stirring often and scraping the pan, for 18 to 22 minutes until the onions are deep golden and very soft.

Lower the heat if they start to scorch before they have browned evenly.

Ingredients
  • 1 tbspOlive oil
  • 12 oz total for recipeYellow onions
  • 1/2 tspKosher salt
  • 1/4 tspBlack pepper
  • 1 tspGranulated sugar
Step 2

Finish the onion filling

~2 min

Finish the onion filling.

Stir in 2 tbsp beef broth and 1 tsp balsamic vinegar, then cook 1 to 2 minutes more until the liquid evaporates and the onions look glossy and jammy rather than wet.

Transfer to a bowl and spread into a thin layer so it cools slightly; this keeps the sandwiches from steaming the bread too much.

Ingredients
  • 4 slices total for recipeSourdough bread
  • 12 oz total for recipeYellow onions
  • 2 tbspBeef broth
  • 1 tspBalsamic vinegar
Step 3

Build the sandwiches

~5 min

Build the sandwiches.

Spread 1 tsp Dijon mustard across two slices of sourdough bread.

Divide the onion mixture over those slices, then top with 4 oz shredded Gruyere and 2 oz shredded provolone, dividing the cheese evenly so it melts into the onions.

Cap with the remaining bread slices.

Ingredients
  • 4 slices total for recipeSourdough bread
  • 12 oz total for recipeYellow onions
  • 1 tspDijon mustard
Step 4

Butter the exterior

~5 min

Butter the exterior.

Spread 2 tbsp softened unsalted butter over the outside of all 4 bread slices, using all of it and getting it right to the edges for even browning.

Keep the filling inside the bread and press the sandwiches together lightly so they hold together in the pan.

Ingredients
  • 4 slicesSourdough bread
  • 2 tbspUnsalted butter, softened
Step 5

Grill the first side

~5 min

Grill the first side.

Set a large skillet or griddle over medium-low heat.

Cook the sandwiches for 3 to 5 minutes on the first side, pressing gently with a spatula once or twice, until the bread is deep golden brown.

If the bread browns too quickly, reduce the heat before flipping.

Ingredients
  • 4 slices total for recipeSourdough bread
Step 6

Flip and melt through

~7 min

Flip and melt through.

Turn the sandwiches carefully and cook the second side for 3 to 5 minutes more, covering the skillet for the last 1 to 2 minutes if needed to help the cheese fully melt.

The finished sandwiches should feel hot and the cheese should be fully soft and stretchy when cut.

Step 7

Rest, slice, and serve

~3 min cook

Rest, slice,

Transfer to a cutting board and rest for 2 to 3 minutes so the cheese settles slightly and the layers do not spill out

Step 8

Slice each sandwich in half

After ~3 min

Slice each sandwich in half

Step 9

Serve meal

~1 min

Once all dishes are cooked and ready, plate and serve the meal together.

French onion grilled cheese: serve.

French onion grilled cheese: serve immediately while the crust is crisp and the onion filling is still warm and savory.

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Ingredients

For 2 people

  • 4 slices sourdough bread
  • 2 tbsp unsalted butter, softened
  • 1 tbsp olive oil
  • 12 oz yellow onions, thinly sliced
  • 1/2 tsp kosher salt
  • 1/4 tsp black pepper
  • 1 tsp granulated sugar
  • 2 tbsp beef broth
  • 1 tsp balsamic vinegar
  • 4 oz Gruyere cheese, shredded
  • 2 oz provolone cheese, shredded
  • 1 tsp Dijon mustard

Method

  1. Caramelize the onionsHeat 1 tbsp olive oil in a 10-inch skillet over medium-low heat. Add 12 oz thinly sliced yellow onions, 1/2 tsp kosher salt, 1/4 tsp black pepper, and 1 tsp granulated sugar. Cook, stirring often and scraping the pan, for 18 to 22 minutes until the onions are deep golden and very soft. Lower the heat if they start to scorch before they have browned evenly.
  2. Finish the onion fillingStir in 2 tbsp beef broth and 1 tsp balsamic vinegar, then cook 1 to 2 minutes more until the liquid evaporates and the onions look glossy and jammy rather than wet. Transfer to a bowl and spread into a thin layer so it cools slightly; this keeps the sandwiches from steaming the bread too much.
  3. Build the sandwichesSpread 1 tsp Dijon mustard across two slices of sourdough bread. Divide the onion mixture over those slices, then top with 4 oz shredded Gruyere and 2 oz shredded provolone, dividing the cheese evenly so it melts into the onions. Cap with the remaining bread slices.
  4. Butter the exteriorSpread 2 tbsp softened unsalted butter over the outside of all 4 bread slices, using all of it and getting it right to the edges for even browning. Keep the filling inside the bread and press the sandwiches together lightly so they hold together in the pan.
  5. Grill the first sideSet a large skillet or griddle over medium-low heat. Cook the sandwiches for 3 to 5 minutes on the first side, pressing gently with a spatula once or twice, until the bread is deep golden brown. If the bread browns too quickly, reduce the heat before flipping.
  6. Flip and melt throughTurn the sandwiches carefully and cook the second side for 3 to 5 minutes more, covering the skillet for the last 1 to 2 minutes if needed to help the cheese fully melt. The finished sandwiches should feel hot and the cheese should be fully soft and stretchy when cut.
  7. Rest, slice, and serveTransfer to a cutting board and rest for 2 to 3 minutes so the cheese settles slightly and the layers do not spill out. Slice each sandwich in half and serve immediately while the crust is crisp and the onion filling is still warm and savory.

Before you cook

What to get ready

Cutting board, bread knife, skillet or sandwich press if the method calls for toasting, and spatula.

Caramelize onions fully before assembling and grate the cheeses for even melting.

If something needs adjusting

Sandwich filling slides out

Drain excess onion liquid and use a thin layer between the cheeses.

A larger sandwich is difficult to eat

Use thin, even layers and avoid overfilling. Cut only after fillings have settled briefly, and serve toasted versions promptly.

Store for later

Store perishable fillings refrigerated separately from bread when practical. Keep packed cold sandwiches chilled; reheat cooked leftovers to 165°F before assembling hot versions.

Refrigerate perishables within 2 hours, or 1 hour above 90°F. Keep the fridge at 40°F or below; use refrigerated leftovers within 3–4 days. USDA storage and reheating guidance.

Make the ingredients go further

Use extra caramelized onions as a pizza topping.

Next use for your ingredients: Caramelized onion pizza →

Calculate this meal with your own prices →

How to Caramelize Onions →

Cooking notes updated October 24, 2026. How we create recipes.

Tips, swaps and questions

A little kitchen know-how

For the deepest flavor, cook the onions patiently over medium-low heat and do not rush the browning. If the pan looks dry before the onions are fully amber, add a teaspoon of water or broth and scrape up the fond. A mix of Gruyere and provolone gives you both nutty flavor and a cleaner melt than using Gruyere alone.

Make it work for you

If you do not have Gruyere, use Swiss cheese plus a little mozzarella for stretch, but expect a milder, less nutty sandwich. If you want a vegetarian version, replace the beef broth with mushroom broth or water plus a few drops of soy sauce; the onions will still be rich, but the savory depth will change slightly.

Use more of your sourdough bread and provolone cheese in ham cheese panini.

Can I make the onions ahead of time?

Yes. Caramelized onions can be cooked up to 3 days ahead and refrigerated in a covered container within 2 hours of cooking. Rewarm them briefly before assembling so they spread easily and do not chill the bread too much. Once assembled, the sandwiches are best cooked right away for the crispest crust and the most even melt.

Times are estimates. Check ingredients for allergens. For safe temperatures and storage, see FoodSafety.gov.

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