soap holder on ceramic tile bathtub wall

The porcelain soap holder on my tile wall above the bathtub has come off. It seems to have been installed in the wall with plaster-of-paris originally and has broken/cracked. Question: Must I break up all the plaster of paris in the hole (in the wall), then reinstall with new plaster? Or, would it be possible just to cement it back in with tile cement (adhesive)?

Lloyd

All of the old mortar should be chipped out of the hole and off the back of the dish. The dish should be installed with new mortar. Use duct tape to secure the dish until the new mortar dries (overnight).