Brown Sugar Apple Cider Gastrique

A gastrique is a caramelized sugar deglazed with an acid and reduced to form a sauce.
So essentially sugar + acid, reduced over heat = delicious sweet and sour sauce.
The sugar can be white, brown, honey, maple syrup, molasses, etc.
The acid can be apple cider vinegar, red wine vinegar, balsamic vinegar, lemon juice, orange juice, etc.
Gasteiques pair particularly well with fatty dishes as both the sugar and acid help to counteract some of the fat.

Brown Sugar Apple Cider Gastrique
brown sugar
water
apple cider vinegar

Put the brown sugar in a pot with a little water. The water just helps to melt down the sugar smoothly without it burning. Put over medium heat and melt, shaking the pan often, until the sugar liquefies. Add an equal amount of vinegar as sugar and reduce over high heat until the mixture thickens just enough to coat a spoon. That's it! 
Trickiest part is ensuring it doesn't burn, reduces enough, but not too much!