I agree with
@JCinFLA.
I know getting "closer to the source" seems like a logical idea.
But (yes; that's a big but), that is introducing even more "unknowns" into the inhalation safety hodgepodge.
It may "seem" like it should work. But, one has no idea if the components extracted, will still replicate the flavor desired. They could be entirely absent. Or, they may not vaporize at the temperatures we vape at. And, that says nothing about the exposure one may be submitting themselves to.
I will be one of the first to admit that we really don't know what risks we take vaping; as there has been almost nothing in the way of long term studies. Let alone, for all the multitude of various flavor compounds. The possible combinations are near limitless. But when one introduces their own extraction, and filtering processes, I can't help but think that risk is magnified.
I am not saying any given commercial concentrate is automatically safer... because I don't know. I am only saying; that it is likely that one is adding to the risk (because of additional unknown ingredients/components). Ultimately, it comes down to, what is it worth to you? Have you eliminated all other alternatives? Is this the one thing that keeps you from returning to smoking? Is this less risky than smoking?
I don't know any given person's answers; and I don't judge them for their answers, or choices. I have enough to answer for, in my own life.
I understand that concentrates get a bad rap because they are not "natural." But, I choose to look at them, as a "cleaner" source... if for no other reason, than they contain nothing not absolutely necessary to replicate the flavor desired. (Rational: ingredients cost money. Don't add anything unneeded. Fewer ingredients = greater profits... as long as the result tastes good.)
And, also as JC already pointed out; there are a bunch of options already out there... before one should feel obligated to reinvent the wheel. Bull City Flavors is just one vendor. And, if you do a search for "Chocolate," you will find no less than 70 results. Granted, some are for wholesale size duplicates. But, still, that leaves you with more that 30 offerings... including a couple "chocolate double" choices. 
@catilley1092, if you don't feel comfortable asking your local shop for the recipe, you might at least want to ask them if they
extract any of their own flavors? And, if they do, is chocolate one of them? At least, before you yourself, drive down that road.
And, if you decide to explore various concentrates, keep in mind that often there are other secondary flavors that "enhance," "boost," "fill out," or "complete" a desired profile.
When you taste various chocolate concentrates; don't just look for "yes/no" perceptions. Instead, look for what tastes "good," as well as what might be "bad" or missing. Often, a combination of two, or more, ingredients is necessary to fulfill a flavor "profile."
Finally, I would hope to offer
reasonable expectations, for a "chocolate" search. Chocolate is one of the "unicorn" flavors for many mixers... it is highly sought, and rarely found. That said, you have had a chocolate vape you liked, and therefore... should be achievable.
- Buy only the smallest volumes available of concentrates until you dial in those that work best for you. You can always buy bigger bottles later.
- Consider combinations. "This" flavor has the right "smooth and creamy," but not enough "chocolate." While, "that" flavor has a lot of "chocolate" taste, but it s dry and chalky. It may be simply a matter of combining the two. Or, the addition of yet another concentrate... like a cream, or a sweetener. Keeping an open mind, allows for a lot more options, than a simple this is "right/wrong.
- If this is really important to you; don't get discouraged. I like to think about a couple of things attributed to Thomas Edison:
- "Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time."
- "Just because something doesn't do what you planned it to do doesn't mean it's useless."
- "I have not failed. I've just found 10,000 ways that won't work."
Bottom line? If it is truly important to you; keep at it. Your local shop figured it out, so can you,... if you want to bad enough.
