Grilled Cheese with Balsamic Onions
To make onions, cut into ⅛” half circles. Heat over low the olive oil in a skillet. Place sliced onions in skillet and begin to let onions cook- do not stir. Continue to cook onions until they begin to brown, 10-15 minutes. Once onions are cooked, stir in balsamic vinegar and continue to cook until vinegar reduces down, about 5 minutes.
Preheat griddle over low heat. Assemble the sandwiches by spreading 1 tablespoon of mustard on one slice of bread. Layer half the onions, bacon, followed by half the cheese and top with second slice of bread. Repeat with second sandwich.
Brush the top of the sandwich with olive oil and place that side down on pan. Brush the top side of the sandwich with olive oil. Grill on each side until browning and cheese is melting, 3 to 5 minutes per side. Repeat for second sandwich.