Hello My name is Matt and I have undertaken a tiled shower for my wife. The question I have is about the mortar/cement on top of the liner pan. Is there a certain type that is preferred in this final step to building the pan?

Hi Matt
The mixture for the top layer is just "Sand Mix" which you can get at any building supply store. It's mixed with water to create what is called "Deck Mud" .... a slightly moist mixture, just moist enough to cling in a ball when squeezed. If it's mixed too wet it'll be no good.
It should be finished off to a thickness no less than 1-1/4".