# Components:
→ 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
# Directions:
01 - Heat 1 tablespoon butter and 1 teaspoon olive oil in a skillet over medium heat. Add sliced onions and 1/4 teaspoon salt. Cook, stirring occasionally, for 15-18 minutes until golden brown and caramelized. Add 1/2 teaspoon sugar halfway through if desired for deeper sweetness. Set aside.
02 - Lay out all 4 sourdough slices. Butter one side of each slice with softened butter.
03 - Place half the Gruyere cheese on the unbuttered side of two bread slices. Top each with half the caramelized onions, then sprinkle with thyme or black pepper if using. Cover with remaining cheese and top with the other bread slices, buttered side facing outward.
04 - Heat a large skillet or griddle over medium-low heat. Place sandwiches in the pan and cook for 3-4 minutes per side, pressing gently, until bread is golden brown and cheese is completely melted.
05 - Remove sandwiches from pan and let rest for 1 minute. Slice diagonally and serve hot.