welding copper to stainless steel?

A friend has claimed that it is possible to fusion weld copper to 
stainless steel. I have searched for it and found a few mentions of 
brazing copper to stainless and a few sites that say it can be fusion 
welded, but no details. Can anybody point me to a site or explain how it 
is done? I did not think it was possible and am still pretty skeptical.

Thanks,
BobH