display archive as collapsing links

I would like to output the following

- 2015
  -October
     - my post is good
     - another post
  September
- 2014
 - January
  -February

I want to be able to output a nested listed of the archives - note: I am not using widgets so will be code if possible.

I can handle the expand collapse but need to output the list and preferably by post category.