Caramelized Onion Gruyère Cheese (Printable)

Toasted bread layered with melted Gruyère and sweet, golden caramelized onions.

# Ingredient List:

→ 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

# Directions:

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 an additional 2 to 3 minutes. Remove from heat.
02 - Spread softened butter on one side of each bread slice. Place two slices, butter-side down, on a work surface. Distribute half the grated Gruyère cheese evenly over the bread. Top with caramelized onions, then the remaining Gruyère cheese. Close each sandwich with the remaining bread slices, butter-side up.
03 - Heat a nonstick skillet or griddle over medium heat. Place sandwiches in the skillet and cook for 3 to 4 minutes per side, pressing gently, until bread is golden brown and cheese is melted. Lower heat if bread browns too quickly before cheese melts.
04 - Slice sandwiches and serve immediately.

# Expert Advice:

01 -
  • The caramelized onions do all the heavy lifting, turning something humble into something that tastes like you spent hours in the kitchen.
  • Gruyère has this nutty depth that plain cheddar can't touch, and it makes the whole sandwich feel somehow more grown-up without being fussy.
  • It's ready in under an hour, which means you can pull off restaurant-quality comfort food on a weeknight without any real stress.
02 -
  • Don't rush the onions—this is the one place where time is actually an ingredient, and cutting corners here means you'll end up with something that tastes like regular grilled cheese with some onions thrown in.
  • Use a gentle hand when spreading the softened butter; if you press too hard, you'll tear the bread, and if you use cold butter straight from the fridge, you'll bruise the bread trying to spread it.
  • The sandwich will continue to cook slightly after you take it off the heat, so if the cheese looks almost melted, that's actually the perfect moment to pull it off the skillet.
03 -
  • If your softened butter is too soft and your bread tears, pop it in the freezer for a few minutes—it'll firm up just enough to spread without ripping the slice.
  • Make the caramelized onions ahead of time and store them in the fridge for up to five days; they actually taste even better the next day once the flavors have settled.
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