Boil on low heat:

• one part balsamic vinegar
• one part of maple syrup
  until sauce is reduced and becomes thick.
  Serves well on fish, shrimps, other seafoods and salads.
  (My niece adds a dollop of Dijon mustard, but online, most recipes don't)
  Here's one that does (no, I haven't tried it myself):

Maple-Balsamic Vinaigrette Recipe - Allrecipes.com

https://www.allrecipes.com/recipe/159976/maple-balsamic-vinaigrette/

• Place vinegar, maple syrup, Dijon mustard, salt, and pepper into a blender. Pulse to combine, then add the olive oil in a steady stream with the motor running.