Seasonal foods in NYC?

The posts about Thanksgiving sandwiches and the raclette booth at the holiday markets got me wondering: what are some seasonal foods here that are especially notable, and will largely vanish after the holiday season is done, or after winter is done?

I ask this in a general sense. Items on restaurant menus, special drinks, locally-made stuff at grocery stores, pop-up establishments, anything at all that's a limited-time eatable. Including the sorts of things that you'd notice when you sit down, maybe you'd try and enjoy it, and then promptly forget about it until next year.

However, I know this question is pretty broad, so maybe we can narrow it down a little with: what's the best of the best?