Hi,if you want to try & keep the shape of the toadstool,then I would frag it using the donut method.You basically cut about a 1" circle(or larger depending on size of coral)around the entire head of the colony.This ends up giving you a donut ring shaped piece of coral.You can then sub-divide this into suitable sized frags.The parent colony will still retain it's basic shape (it will look pretty sorry for a few days)& will eventually grow new polyps from the entire cut area.HTH