I'm guessing it's the egg nog i'm tasting up front,it's that spicy type taste,i think it's probably the nutmeg from the egg nog,but this was my first time using the Bourbon vanilla too,so it could be something in that also.My palate isn't that great to detect exactly where it's coming from haha.
It could very well be the Vanilla Bourbon. That stuff is potent (and super dark). I'm pretty sure that's what multiplies the "gunk-factor". I was really going for a fairly complex vanilla flavored custard, though, so I felt like it just had to be there.