I'm actually not even certain how to harvest. I guess the greens can be used as green onions, but do you eat the sets at the top? Or is there a bulb in the ground? (something something meme...but now I'm too afraid to ask)
I believe the whole plant is edible, but I was planning on pulling the plant for the bulbs (which should be shallot sized) and re-planting the sets for next year.