Caramelized Onion Gruyère Cheese (Printable Page)

Golden slices with melted Gruyère and sweet caramelized onions for a rich, savory sandwich.

# What You Need:

→ Caramelized Onions

01 - 2 medium yellow onions, thinly sliced
02 - 2 tbsp unsalted butter
03 - 1/2 tsp kosher salt
04 - 1/4 tsp freshly ground black pepper
05 - 1/2 tsp sugar (optional)
06 - 1 tsp balsamic vinegar (optional)

→ Sandwich

07 - 4 slices rustic sourdough or country bread
08 - 2 tbsp unsalted butter, softened
09 - 5 oz Gruyère cheese, grated
10 - Caramelized onions (prepared above)

# Steps:

01 - Melt 2 tbsp unsalted butter in a large skillet over medium-low heat. Add sliced onions, salt, and pepper. Cook, stirring occasionally, for 25 to 30 minutes until deeply golden and caramelized. Stir in sugar and balsamic vinegar if using; cook for an additional 2 to 3 minutes. Remove from heat.
02 - Spread softened butter evenly on one side of each bread slice. Place two slices butter-side down and distribute half the grated Gruyère over them. Spoon caramelized onions atop the cheese, then sprinkle remaining Gruyère. Close each sandwich with a buttered slice, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Cook sandwiches for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese melts. Lower heat if bread browns before cheese is fully melted.
04 - Slice sandwiches and serve immediately while warm.

# Expert Advice:

01 -
  • Those caramelized onions taste like they took hours but really only need your occasional attention.
  • Gruyère melts into something richer and more elegant than cheddar ever could be.
  • It's fancy enough to serve to someone you're trying to impress, but easy enough for a solo lunch.
02 -
  • Low heat and patience with the onions are everything; rushing them over high heat just browns them without developing that deep sweetness.
  • Don't skip grating the cheese yourself—pre-shredded cheese has anti-caking agents that prevent it from melting as smoothly.
03 -
  • Keep the heat medium, not high—high heat will burn your bread before the cheese inside even realizes what's happening.
  • If you're cooking for a crowd, caramelize your onions ahead of time and reheat them gently just before assembling; the sandwich itself only takes 10 minutes.
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