To make the granita, pour the water and sugar into a small pan and bring to the boil, add the white wine, reduce the heat and simmer for approx. 2 mins. Remove the pan from the heat, allow to cool a little. Roughly chop the herbs, setting aside approx. 1 tbsp for the garnish. Place the remaining herbs in a bowl, pour over the sugar syrup and leave to stand for approx. 10 mins., allow to cool completely. Pour the liquid through a fine sieve into a shallow dish.
Cover and freeze the mixture for approx. 5 hrs., scrape the mixture four times with a fork until frozen.
Wash the kohlrabi, remove the leaves, place on a baking tray lined with baking paper. Beat the egg whites until stiff, mix in the salt and flour.
Using your hands wrap the salt dough around the kohlrabi like a snowball, return to the tray.
Bake for approx. 1 1/2 hrs. in the centre of an oven preheated to 160°C.
Allow the kohlrabi to cool a little, remove the salt crust using a hammer. Peel the kohlrabi, slice thinly and arrange on plates. Roughly chop the hazelnuts, scatter over the top, drizzle with the nut oil, season. Serve with the herb granita, garnish with the reserved herbs.