You might be referring to the string muting I do by placing the palm of my picking hand lightly on the strings right near where they cross the saddle. I explain this in detail on my "Easy Steps to Guitar Fingerpicking" and on other fingerpicking lessons
as well. Aside from that, I can't think of anything else I do to get what you call a "choppy" sound.
It sometimes takes some practice to find the "sweet spot" where the notes are damped but still have some tone. Work at it a while and you should be able to get it.
I hope this is a help to you. Let me know if you have any more questions.