COOK restaurant is a tiny storefront in the heart of downtown St Helena, and it was amazing.  Some of the best (spicy) tomato sauce I have ever tasted, fantastic duck breast risotto, a very intriguing wine list-we had an Italian verdecchio that was almost saline in its bracing minerality and a nice red as well-and not ridiculously priced.  Great service.  Tiny, quirky, if slightly dark bistor-style interior. 
A definite recommendation!
				

