Here's a video taken by my wife.
Chopstick Scissors ~ by PGA
I actually learned from my mum. When I was young, I saw her do it while feeding me and decided to emulate. It's really just a "scissor action": the chopsticks grip the noodles and then each chopstick goes in opposite direction just like a scissor. Try it with one noodle fist and then to more noodles.