To add a launcher item that runs a single specific virtual machine we can create a new launcher item as it is described here for 11.10.
In short, to start a Virtual Box machine without the Virtual Box Manager we may add the following command to start the VM in the
Exec= section of the
Name=the name you want shown
Exec=VBoxManage startvm 'name of the machine'
Proceed as it is decribed in the answer linked above. You will also find solution for other Ubuntu versions there.