This half-baked (or perhaps, half-boiled?) idea is pretty
much Exactly What It Says On The Tin. First, extract
juice from a pumpkin, then remove water from the
juice until it's viscosity is similar to maple syrup. That's
it! :)
Probable uses of this imagined ingredient could be
many: in
mixed drinks, in cakes or pies, on or in ice
cream... anywhere you might use a flavored syrup, you
could use pumpkin reduction.
Ok, for a bit more elaboration: there are a few
different ways of getting juice from a pumpkin, some of
which don't even involve buying / growing any more of
our main ingredient than we otherwise would.
First, start by doing preparations for making pumpkin
pie from fresh pumpkin... However many pie than you
would normally cook around the Thanksgiving /
Christmas season, but you must have a recipe which
uses fresh pumpkin, not canned.
The first step in most pumpkin pie recipes is to remove
and discard the guts of the pumpkin. For making
pumpkin reduction, take the pumpkin guts out of the
pumpkin, cook them slightly (to increase juice
extraction), then put them into a vegetable juice
extractor; discard the solids, and put the liquid in a pot
on the stove, and start reducing that liquid down to a
syrup.
The second step of pumpkin pie making is generally to
cut up the pumpkin flesh, then bake it. For this idea,
make sure that the pumpkin chunks are on a wire rack,
raised high enough above a roasting pan that, while
cooking, they won't sit in the juice which comes out.
After baking, pour this liquid into the pot, stirring it
into the (slightly reduced) pumpkin gut juice.
Third, take a small portion of the baked pumpkin flesh,
and run it through the juice extractor. Stir the liquid
into the pot, and put the solids with the rest of the
baked pumpkin. This will result in a slightly dryer
pumpkin pie, which IMHO is a good thing (I've seen
many pumpkin pies which have a puddle of liquid on
top, which is rather unappealing). If you think the pie
will be too dry, replace some or all of the removed
liquid with apple juice or cider.
Finish making the pumpkin pie, and continue cooking
the liquid until it reaches the right viscosity.
Note that there is only *one* ingredient in this pumpkin
reduction: pumpkin (juice)!
Obviously if you really want to, you could add some
pumpkin pie spice to it, but be careful not to add too
much, or the flavor might overpower the pumpkin.