Getting this play style requires you to get stealth kills using any type of knife (though it's unconfirmed if the shiv on Skurky's Law counts). Theres a knife on almost every level so it's just a matter of finding it.
A Personal Contract - Gound Floor may be the easiest. Take the knife out of the kitchen and kill the chef. Go into the hall beyond and wait for the conversation to play out before killing the next guard. Kill the guard upstairs and then restart the checkpoint. Probably not the most efficient but it'll get you there.
