Blue Note is a blend of Virginia & mild Cavendish tobaccos, so that doesn't mean much...any Virginia/Cavendish extract would give you those flavor notes most likely....but it may be a clue.
I'm firmly convinced that one of the key ingredients is a tobacco extract of some type. I've been playing around with some PA Tobacco Absolute, and I think it MIGHT be one of the missing elements...it has a lot of the hallmarks of Bobas that seem to be missing in some of the recipes.....but Tobacco Absolute is some REALLY strong stuff, so working out dilutions of it are taking a bit of time. It looks like molasses (makes VG look thin in comparison), and has some fine particulate matter that some people have noted in Boba's.
Right now I've gotten down to two drops of TA per 5ml of VG as a substitute for Black Cigar, and I may still have to dilute it further, but I think this is getting closer to the Holy Grail... it has that certain "Something" that seems missing using Black & Mild or Black cigar. I like it a lot, I just have to figure out what the correct dilution factor needs to be, but it takes at least a week or two of steeping to really gauge how close it is, because, like Bobas, it keeps changing over the first few weeks.
Nevertheless...it's a nice vape.. (recipe #7 substituting TA dilution for Black & Mile Plus)