Caramelized Onion & Gruyère Grilled Cheese (Printable)

Sweet caramelized onions and nutty Gruyère melted between crispy golden bread for a gourmet twist on a classic favorite.

# What You Need:

→ 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

# How-To Steps:

01 - Melt butter with olive oil in a large skillet over medium-low heat. Add sliced onions, salt, and pepper. Cook, stirring occasionally, until deeply golden and caramelized, about 25–30 minutes. Stir in thyme and balsamic vinegar during the last minute.
02 - Lay out bread slices. Spread caramelized onions evenly on two slices. Top each with half the grated Gruyère. Close with remaining bread slices.
03 - Spread softened butter evenly on the exterior sides of each sandwich.
04 - Heat a non-stick skillet or griddle over medium heat. Place sandwiches in pan and cook until golden brown with melted cheese, about 3–4 minutes per side. Press gently with spatula for even toasting.
05 - Slice sandwiches in half and serve immediately while hot.

# Expert Advice:

01 -
  • The caramelized onions become candy-sweet and deeply savory, transforming a simple sandwich into something that feels like it came from a French bistro
  • Gruyère adds this incredible nutty richness that pairs perfectly with the sweetness of the onions, creating layers of flavor in every bite
02 -
  • Rushing the caramelization process is the biggest mistake you can make—truly golden onions need at least 25 minutes to develop their sweetness
  • Don't overcrowd your pan when cooking the sandwiches, or they will steam instead of developing that crucial crispy exterior
03 -
  • Grate your own cheese from a block rather than using pre-shredded cheese, which contains anti-caking agents that prevent smooth melting
  • Use a spatula to press down gently but firmly while cooking—this ensures the cheese melts completely and bonds the sandwich together
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