Caramelized Onion & Gruyère Grilled Cheese (Printable)

Sweet caramelized onions and nutty Gruyère melted between crispy golden bread for a French-inspired twist on a classic comfort favorite.

# Ingredient List:

→ Caramelized Onions

01 - 2 large yellow onions, thinly sliced
02 - 2 tbsp unsalted butter
03 - 1 tbsp olive oil
04 - 1/2 tsp salt
05 - 1/4 tsp freshly ground black pepper
06 - 1 tsp fresh thyme leaves
07 - 1 tsp balsamic vinegar

→ Sandwich Assembly

08 - 4 slices rustic country bread
09 - 4 oz Gruyère cheese, grated
10 - 1 tbsp unsalted butter, softened

# Directions:

01 - In a large skillet over medium-low heat, melt the butter with the olive oil. Add the sliced onions, salt, and pepper. Cook, stirring occasionally, until the onions are deeply golden and caramelized, about 25–30 minutes. Stir in thyme and balsamic vinegar, if using, and cook 1 minute longer. Remove from heat.
02 - Lay out the bread slices. Evenly spread caramelized onions on two slices. Top each with half of the grated Gruyère. Place the remaining bread slices on top to close the sandwiches.
03 - Butter the outside of each sandwich with the softened butter, ensuring even coverage for golden crisping.
04 - Heat a non-stick skillet or griddle over medium heat. Place the sandwiches in the pan and cook until golden brown and the cheese is melted, about 3–4 minutes per side. Press gently with a spatula to ensure even toasting.
05 - Slice each sandwich in half diagonally and serve immediately while hot and crispy.

# Expert Tips:

01 -
  • The way the sweet onions balance the sharp, nutty Gruyère is pure magic
  • It transforms everyday ingredients into something that feels fancy enough for company but easy enough for Tuesday
  • That first crunch of perfectly toasted bread followed by gooey, cheesy perfection never gets old
02 -
  • Do not rush the onions, they need time to develop that deep, sweet flavor and golden color
  • Low and slow is the secret to perfectly melted cheese without burning the bread
  • Let the sandwiches rest for about 30 seconds after cooking so the cheese sets slightly
03 -
  • Patience with the onions pays off in flavor, resist turning up the heat
  • A cast iron skillet creates the most evenly golden, crispy exterior
  • Letting the cheese melt completely before flipping prevents slipping and sliding
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