Place the shredded white and red cabbage in a large bowl. Finely slice the red onion into half rounds, and then grate (or julienne, if you can be bothered) the carrots and add both to the bowl. In another bowl or jug/pitcher, mix together the water, white wine vinegar, icing/confectioners’ sugar and salt. Pour over the cabbage, then cover the bowl and shake well. Leave for at least one hour, ideally two – shake it once in a while. You’re lightly sousing the cabbage, ensuring it is easier to eat and digest.