Is the board over stud or blockwork? And.... has it been skimmed?
Building out with cement or adhesive, is going to put a strain on the weight limit of what plasterboard can hold (32kg's per sqm). at 10mm depth, you're looking at adding an extra 16-18kg per sqm. leaving only 14-16kg allowance for the tiles and adhesive bed.
Bal Quickset render "might" work, but it doesn't specify it can be done on the bag. I just gave Bal a ring and they'd never heard of anyone rendering plasterboard so its an "at own risk" scenario.
The correct thing to do really is either
1. take the plasterboard off and pack out the stud with a full height timber packer by 5-10mm as required
2. adjust the whole stud frame and move it forward or back as required
or 3. depending on the wall setup, overboard by mechanically fixing extra plasterboard, marmox or Hardie over the top, screwing into the studwork (if you can find it) or anchoring it into the breezeblock/render/brick behind.