Caramelized Onion Gruyère Cheese (Printable)

Golden bread slices filled with nutty Gruyère and deeply caramelized onions for rich, comforting bites.

# What You'll Need:

→ Caramelized Onions

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

→ Sandwich

07 - 4 slices rustic sourdough or country bread
08 - 2 tablespoons unsalted butter, softened
09 - 5 ounces Gruyère cheese, grated
10 - Caramelized onions from above

# How-To Steps:

01 - Melt 2 tablespoons 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 onions are deeply golden and caramelized. Stir in sugar and balsamic vinegar if using; cook for 2 to 3 more minutes. Remove from heat.
02 - Lay out bread slices and spread one side of each with softened butter. Place two slices butter-side down and evenly distribute half the Gruyère cheese over them. Spoon caramelized onions over the cheese, then top with the remaining Gruyère. Close each sandwich with another bread slice, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place sandwiches in skillet and cook for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese is melted. Reduce heat if bread browns too quickly before cheese melts.
04 - Slice sandwiches and serve immediately.

# Expert Advice:

01 -
  • Caramelized onions transform ordinary into restaurant-quality without any fussy technique.
  • Gruyère's nutty, complex flavor feels luxurious but costs the same as basic cheddar.
  • The whole thing takes less than an hour and feels like you've been cooking all day.
02 -
  • Don't skip the low heat for caramelizing onions, as high heat will brown them quickly but taste bitter instead of sweet and complex.
  • The optional sugar and vinegar do something almost magical; I hesitated the first time, but they genuinely deepen the whole flavor profile.
03 -
  • Toast a few fresh thyme leaves with the onions in the last minutes of cooking, and you'll understand why French cooking takes these combinations so seriously.
  • Serve this with a simple green salad or tomato soup, and suddenly you have a complete meal that tastes like you've been in the kitchen for hours.
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