I encountered the same dish as you in culinary school. A 90 year old balsamic was used. It was in a small tabasco sized bottle and cost like about $90 which was a lot in the early 80's. That dish was definitely a major "aha" mind expanding moment in my culinary journey. It was the inspiration for the ice cream which I used occasionally on degustation menus at my restaurant. I take a quality traditional balsamic vinegar and reduce it au sec. Then temper into a fairly basic ice cream base. That's it!