Wow, I never thought of that...I guess start researching old-fashioned directions on how to make butter from raw cow's milk and see what happens if you use breastmilk instead.
Maybe the Weston A. Price website might have a link, some of the traditional foods info.
---------- Post added at 03:53 AM ---------- Previous post was at 03:48 AM ----------
Meant to add...I've sorta made butter from overwhipping heavy cream. In that case, I was trying to shake it in the carton since I didn't have a proper mixer, and I shook and shook, and it got thicker, and all of a sudden, there was a thunk, and a bunch of the fat was lumped together as butter, separated from the whey, instead of being a nice foamy whipped cream.
I'll bet you might get results faster if you let your milk settle and then pour off the fat...ooh, maybe use a gravy cup, since that's designed to pour off the liquid from the bottom, leaving the fat behind....it's like a measuring cup but with a spout on the bottom...can't remember the proper term for it...a gravy separator? gravy boat?