We'll remove the stem (also known as the peduncle) and the pith, which has almost no flavor.
Pull out your piping bag tips. We want the biggest one (top one on the 2nd column).
Here's a better look at our "tool."
Grab all of the leaves (calyx) together and pull them off.
This is what you're left with so far.
Insert the piping bag tip straight down around the stem.
Twist about a quarter turn and remove while tilting it sideways.
Here's a video showing the technique. I hope it's appreciated because I damn near dropped my iPhone.
Typically, the whole pith will come out with it.
Here's the end product. Nothin' but the good stuff. Enjoy!