1. Thinly slice onion. Then heat a pan on medium-high heat. When the pan is hot, add butter and allow to brown, approximately 2-3 minutes. Do not let it burn. Once butter is browned, add onion and saute on medium heat until caramelized and brown, approximately 15-20 minutes. When onions are caramelized, add balsamic vinegar to the onions and saute for 1 minute. Turn off heat

2. Remove the outer rind of the brie. You will be left with the soft center. Mix balsamic-onion mixture into the soft brie, then add salt and pepper. The heat of the onion will slightly melt the brie. Serve immediately with toasted bread or crackers.