Just get a sharp pair of scissors and make a clean fast cut on the base of the Xenia. The left over stalk wil grow into a new stalk.
Place the xenia on a piece of rubble rock, I like to use fish neting or veil, place that over the xenia loosly and rubber band the netting down to the rock.
Place the xenia frag in low flow and it will start to attach in a few days.
To frag even mor off of a stalk, just cut sections out of the top of the crown, like giving it a hair cut and just do the same to do those as the other frags.