- 1 1/2-2 lbs sweet onion, sliced
- 4 Tbsp Olive Oil
- 1/2 tsp fresh thyme leaves
- 2 Tbsp dry sherry
- 1/4 cup Traditional Balsamic Vinegar
- salt and pepper to taste
- 4 slices of rustic bread, like Pain au Levain
- 3 Tbsp salted butter, softened
- 2-3 oz Gruyere, shredded
- For the onions:
- Heat the olive oil in a large saute pan over medium heat. Add the onions and stir to coat. Season with 1/2 tsp salt and 1/2 tsp freshly ground pepper.
- Continue to cook, stirring frequently until the onions begin to turn golden brown. Stir in the thyme, followed by the sherry. Continue cooking until most of the sherry has cooked away and the onions have turned deep golden brown.
- Stir in the balsamic vinegar and continue cooking until the onions have caramelized and the balsamic has completely been absorbed by the onions, being careful not to burn. Remove and set aside. For the Sandwiches:
- Butter each side of bread on one side with the softened butter. Heat a 12" skillet or griddle over medium low heat. Add 1 Tbsp butter to the pan to melt.
- When the butter has stopped foaming, place 2 slices of bread, butter side down, on the pan. Top with half the cheese and 1-2 Tbsp onions. Top with the remaining bread slices, butter side up.
- Gently press down on the sandwich as it cooks. When the cheese has begun to melt and the underside of the bread is toasted, carefully flip each sandwich to toast on the second side.
- Cook until both sides of the sandwich are toasted golden brown and crunchy. Remove from the pan, allow to cool a minute or so before eating, so as not to burn your mouth.