This is a low temperature physicist's parlor trick akin to fire breathing or sword swallowing. It is dangerous - don't do it.
Liquid nitrogen is very cold .
There are three reasons. First, he didn't stay in contact with the liquid nitrogen for very long. The cup had an insulated base to protect his hand. He never touched his lips to the bowl of the cup which is why there was a slurping sound to the toast. And he spit out the liquid almost immediately.