I know it's hard to believe for non-vegans, but delicious vegan pizza exists. As a non-vegan, I eat it regularly instead of normal pizza. My go-to spot is Viva. (This spot is no secret to vegans, and in fact it has been probably 10 years since it was all the rage.)
Viva also has some good (and vegan) chocolatey desserts. So, there is this bakery in Pennsylvania called Vegan Treats. Prior to the giant vegan explosion of the last few years, their baked goods were THE ubiquitous vegan baked goods. And for good reason.
Viva has three chocolatey items from them -- brownies, cookies, and whoopie pies. I can't really get behind the whoopie pies (or basically any whoopie pies), and the cookies are pretty good, but the brownies really shine. They are up there with PeaceFoods and Vegan Divas for best vegan brownies in the city.
Vegan Treats are available elsewhere. They are available a lot of elsewheres. I don't know which of those places sell the brownies. But do yourself a favor and give them a try -- they are delicious even if you are not vegan.
Bottom Line: One of my most-frequented establishments in NYC.