Heat the balsamic vinegar and bring to boil. Simmer and reduce to 1/2 cup. Add (B) and mix well with a whisk and set aside. Heat the pan and add butter. After butter melted, add onion and brown sugar. Sautee till onion is soft and place it in the mixing bowl. Add (A) into the mixing bowl. Pour in salad dressing and toss well. Add pamesan cheese and serve.