You don't need to cut them. If they bunched and you want more you can pull them up and split them up and replant them. I did that last weekend so you may need to wait a while but I wouldn't think it would be too much longer.

Or you can just leave them and harvest later.

Be aware that if you cut the tops too much the white part doesn't get very big so if you want greens then grow chives.

Thanks Shebear.