Chicken sandwiches with brie, shaved Granny Smith apple and Dijon-balsamic reduction on toasted challah

1) In a small saucepan, whisk together vinegar, mustard and honey. Set pan over medium-high heat and bring to a simmer. Simmer until liquid reduces to 120ml, about 3 minutes.

2) Spread mixture on toasted or grilled challah bread slices. Top with brie and then chicken. Using a vegetable peeler, shave apple into thin slices and arrange over chicken. Top with second slice of bread.