You CAN retemper it... but that's another trick...

As for adding liquids, yes, you can put the cream in with the solid and heat both together, or you can add the liquid chocolate to the warmed - not boiling cream. Chocolate should be thoroughly melted by about 80 Deg C.

I bought an expensive little german double walled sealed stainless steel steamer - also good for making proper custards from scratch - without custard powder!.