The first chance you get to do this is in Chapter 1 when you reach the two spawning mounds. First off, do not destroy the spawning mounds.
Let the bambini come on and on the first one grab him with RT and press Y to slam him into the ground. Pick him back up and repeat the same thing. Reason being, you have to have your "mana" or "spirit" gauge full to be able to pull one of the bambini's heads off.
So, when the second bambini comes out, pick him up and press B to pull his head off. When the next bambini comes out of the mound, flick your right stick up so that you will target him. Me personally, I usually wait until he jumps right in front of me to throw the head...because sometimes he dodges and I accidentally blew up one of the spawning mounds that way.
After you kill that one, repeat the same thing, grap one and slam him into the ground with Y which will automatically bring your mana gauge up, grap the next one rip his head off, and the third one hit him with the head.
Very time consuming, but it can be done in the first Chapter.