if by "fob" you mean the remote transmitter, if you have more than one key you can do it yourself. If you only have one key, anyone with vag-com can do it.
If by "fob" you mean the transponder, only volkswagen can tell the immobilizer to recognize a new transponder. That service charge is about $50.
The long & short of it is that there is a numeric access code required to get the immobilizer to recognize new transponders. And no human being is allowed to know what that code is.
They pull your car into a bay, plug it into the diagnostic system, the diagnostic system connects to a computer in wolfsberg over an encrypted link, gets the code, and tells the immobilizer to recognize transponders. Every key you want to be able to start the car with needs to be in the car when they do this, as it starts by erasing it's transponder memory.
On the mk4 platform, there are some ways to figure it out from the vin and some other information.
On the mk5 platform, I've seen one claim that it can be done, but no proof offered.
Passat is a different thing from the golf/jetta platform, but your odds are not good.
As for cutting the key, look for a locksmith who can cut sidewinders. The dealership should be able to sell you keys cut to your VIN for about $65/ea. Plus the programming charge for the immobilizer.
