I've never been to Henry's Hunan, but based on their menu, their offerings don't seem authentically Hunanese. Perhaps I'm wrong.
There's no real Hunanese restaurant to be found in Manhattan (although I've heard that some of the Sichuan places serve Hunanese dishes).
Your best bet is to head to the real deal at Hunan House in Flushing.
137-40 Northern Blvd.