How do I Repair This Broken Chimney Hearth? Brickwork, drystone walling, render are a few subjects covered here. Click here to post questions and get answers

[Jamhan]

What do I use to repair this hearth in from of chimney?
It doesn't have a fire, so doesn't need to be heatproof.
Looking for actual products I can buy - assuming I can't use wall filler on this. Thanks