Unique Version of Prison

[sanfuturo]

I'm trying to find a post-Voldemort war II story in which instead of Azkaban, the prison system is miniaturized - and so are the prisoners! - so the ministry can keep lots of DEs in a small space, and have better control of them, like animals in cages.
In the story, Harry is in charge of Snape, and is quite perverse with him. Being a prisoner, Snape can't refuse any of Harry's advances or orders. I think Harry also threatens to kill him on several occasions.
Thanks for any assistance in finding it!