EFI Boot access denied symbol

Holding down the letter C on the keyboard when you turn on your Mac, should cause it to boot from an already inserted Optical disc that contains a compatible bootable operating system. If you turn on the Mac and then insert the Optical disc, it will not be recognised in time, so you will then need to reboot again with it still in.

You can also hold down the Option/Alt key and the Mac should then switch to displaying a list of all available bootable disks, including any optical disc.

In your case as you want to boot effectively from the MacBook, you could try one of the following two possibilities.

1. Put the installer disc in the MacBook, and make sure the MacBook has DVD/CD sharing enabled (in System Preferences)
2. Boot the Mac mini holding down the Option/Alt key and see if the MacBook disc is listed, obviously both machines have to be on the same network.

or

1. Boot the MacBook Pro in FireWire target disk mode by holding down the letter T when you turn it on (Some MacBook non Pro models do not have FireWire so it may not support this.)
2. Connect the MacBook via FireWire to the Mac mini
3. Turn on the Mac mini and hold down the Option/Alt key

You can do the reverse of the second method assuming your MacBook has FireWire. That is put the Mac mini in FireWire target disk mode, plug it in to the MacBook, and then run the installer on the MacBook. It is better however to do it the first way round as the installer will then know it is supposed to be configuring a Mac mini and not a MacBook.