The butter will rise to the top after a few hours, and you skim it off.
Ive also SIMMERED the pot in oil (veg/olive) or butter directly for 5-10 min.. works great!
Chop/grind it up as best you can before.

Beware..It REEKS!
Its like nothing youve ever smelled before, it stays a while.
If youre worried Mom or Dad might wander in... Id think about it.