When you spent an awful amount of time with nothing but books and resources to offer--one would think you would put it to good use. Jefferson used twenty-eight years to put a library's worth of books into his brain. Both fiction and none. How he stumbled into conjuring different...brews came simply from his research into tea, herbs, brewing.
As a poor single father of the Enchanted Forrest, there weren't any antibiotics lying around. He wanted to empower himself on ways to heal with whatever the forrest had to offer. And while he was on the page? Perhaps a line of defense. With the few items of note that the Elf had graciously brought him, Jefferson gathered a few books that were close to the ones he'd had from his home back in Storybrooke, trying to research the roots, leaves, and their properties. It was important he didn't have any accidents. In the past he was more familiar with minor forms of 'poisoning'. Only enough to put people to sleep. Very basic, non-harmful, but there was really no reason he couldn't expand on that.
He didn't have magic or a sword so he should have a little something extra. "One moment." The hatter replied without turning to look, saving the page on his book on the desk in the corner before moving to the front of the counter to observe the customer. He didn't smile but he was sure not to glare or frown. "Nothing short of earl grey, and nothing more pungent than fruit. We also have a few more herbal sorts. Ginger, sage, and so on. What blends interest you?"