Whats your favorite slow Chopin work, outside of the Nocturnes & Waltzes?
Slow, obscure & challenging is somewhat of a tall order, but a fascinating admixture of all of those combined with some of his most imaginative writing for P&O is his Fantaisie on Polish Airs op.13 which I have had in repertoire for nigh on 35 years but most of the rest of the world seems to treat with inexplicable disdain. (He himself held it in the highest regard, btw.) Suck it & see. It should give you a lot to think about in every respect and much to cherish as much as relish.