Equivalent of Avaya Whisper in Asterisk IVR?


I have been trying to migrate our current Avaya IVR systems to Asterisk

So far all is going well and have managed to migrate all except 1, I am unable to work out how to do the following

We have an out of hours call system which will gather some client details, company name from DTMF key input, then ask the user to say the problem they are having (which is recorded), this is fine up until now, what I then need is the following
1.> I require the IVR to call the on call engineer and play the voice recording to them, they should then be given the option to either press 1 to accept the call or 2 to reject the call
2.> If the call is accepted obviously connect the caller to the on call engineer
3.> If the call is rejected I need to continue with the rest of the IVR which has some other call flow management in there

I assume that I need to fire off some other context which will call the on call engineer and then merge the 2 channels upon accepting, I’m just not sure how to do this

Any guidance would be greatly appreciate