This has been bothering me (a native English speaker) for a long time. It seems almost impossible outside of dialogue to describe the act of unconsciously spitting out a "Tch!" in response to something outrageous, comedic, etc. For example:
Bob tch'ed at Mary's absurd suggestion.
John merely tch'ed at the punchline and returned to his work.
Sally tch'ed and rolled her eyes. "He can't be serious!"
In want of the proper verb or phrase for this action, I often have to resort to just choosing another action for my written character to perform so that I can describe it better. But it's not very real to life.
Best Answer
I would use "chuffed".
chuff n. 1. A sound of or like the exhaust of a steam engine. - v.i. 2. to emit or proceed with chuffs. The train chuffed along.
Webster's Encyclopedic Unabridged Dictionary of the English Language 1996 edition.