Sourdough Grilled Cheese Onions (Printable)

Tangy sourdough, Gruyere cheese, and sweet caramelized onions combine for a melty sandwich delight.

# What You'll Need:

→ Bread & Cheese

01 - 4 slices sourdough bread
02 - 5 oz Gruyere cheese, grated or thinly sliced

→ Onions

03 - 1 large yellow onion, thinly sliced
04 - 1 tablespoon unsalted butter
05 - 1 teaspoon olive oil
06 - 1/4 teaspoon salt
07 - 1/2 teaspoon sugar

→ For Grilling

08 - 2 tablespoons unsalted butter, softened

→ Optional Additions

09 - Fresh thyme leaves or black pepper to taste

# How to Cook:

01 - Heat 1 tablespoon butter and 1 teaspoon olive oil in a skillet over medium heat. Add sliced onions and salt. Cook, stirring occasionally, for 15-18 minutes until golden brown and deeply caramelized. Add sugar halfway through for enhanced sweetness if desired. Transfer to a plate and set aside.
02 - Lay out all 4 sourdough slices on a cutting board. Butter one side of each slice with softened butter.
03 - Place half the grated Gruyere on the unbuttered side of two bread slices. Distribute half the caramelized onions evenly over the cheese. Sprinkle with fresh thyme or black pepper if using. Top each with remaining cheese, then place remaining bread slices on top with buttered side facing outward.
04 - Heat a large skillet or griddle over medium-low heat. Place assembled sandwiches in the pan. Cook for 3-4 minutes per side, pressing gently with a spatula, until bread is golden brown and cheese is completely melted.
05 - Remove sandwiches from pan and let rest for 1 minute. Slice diagonally if desired and serve immediately while hot.

# Expert Advice:

01 -
  • The sourdough's slight sourness cuts through the richness in a way that feels indulgent without being heavy.
  • Caramelized onions transform a simple sandwich into something you'd actually order at a fancy café.
  • It comes together faster than you'd think, making weeknight dinners feel less routine.
02 -
  • Don't rush the onions; that golden-brown stage is where the magic lives, and cutting corners here makes the whole sandwich feel ordinary.
  • The medium-low heat for grilling is non-negotiable—too hot and your bread browns before the cheese melts, leaving you with a crunchy exterior and cold cheese inside.
03 -
  • If your cheese is cold from the fridge, grating or slicing it while still cold actually helps it layer more evenly than room-temperature cheese.
  • Baby arugula or a handful of fresh greens added just before the final slice of bread adds a subtle freshness that nobody expects but everyone enjoys.
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