variation inspired by a comment on this post
3 parts grade-B maple syrup to 1 part dark rum (For this batch, that meant 2 1/4 cups syrup to 3/4 cups rum.) Instructions can be found by following the link above.
from here
Pour three cups of water into a soup pot and mark the level on the end of a wooden spoon or ruler. Empty the pot, pour in 21 cups of unsweetened, unfiltered apple juice (a 1-gallon jug, plus an additional 5 cups) and cook at a high boil until it's reduced to the level you marked on your spoon. (For us, this took a little under 3 hours.)
The syrup will continue to thicken a bit as it cools, and, at this level of reduction, settles at a thick, pourable syrup consistency (it does not get as thick as molasses) when stored in the refrigerator.