Chinese Onion

I didn't know there was a particular onion that was Chinese but that is exactly what I have been given. They're just sprouts at the moment but I have also been told how to plant and harvest them.
What you do is dig a trench about a foot deep, plant the onion sprouts in the trench and just cover the tops of the plant (I was given sprouts from the seeds of last season). As the plants grow you keep covering more of the onion until the trench is entirely filled in. They make medium onions but for the first year or so only the tops should be eaten so the rest of the onion can develop.