Chopping Green Onion

I don't mind chopping green onion using my knife, but someone needs your help. "...A lot of Japanese food uses a lot of chopped green onions. Obviously you can use a knife but I'm sure there's a tool for it. The last time I was in Tokyo, soba stands have boxes and boxes of chopped leeks, which is what I would love to have a tool to do..."
Post in Japanese Food Forum