First wash and peel the beetroot. It is best to wear disposable gloves. Then grate the beetroot into coarse strips on the grater. Peel the red onion, cut into half rings and add. Crack and roughly chop the walnuts, also add. Mix the diced apple with the balsamic vinegar, olive oil, honey, horseradish, pepper and salt and mix with the beetroot. Leave to steep in the refrigerator until ready to eat.