To smoke the fish heat the wood chips in a smoker or kettle barbecue until they start to smoke. (Alternatively, line the bottom of an old wok or saucepan with foil, place your wood chips on the foil and heat over a high gas flame until smoking.) Put the cold fish on an oiled rack that will fit into your smoking device. Cover, reduce the heat to low and leave to smoke for 30 minutes. Remove the fish from the smoker and immediately return to the fridge.
For the beetroot trim the stalks off the beetroot. Wash the beetroot well under cold running water. Place each beetroot variety in a separate saucepan and cover with water. Add 50 ml of the white wine vinegar, 50 g of the sugar, 1 teaspoon of the peppercorns, a bay leaf and a pinch of sea salt to each pan. Bring to a gentle boil and cook over medium heat for about 20 minutes, or until just tender. Drain. While the beetroot are still warm, slip off the skins (wearing latex gloves). Cut into halves, or quarters if large, then toss with the chardonnay vinegar, olive oil and some salt and freshly ground black pepper. Set aside.
For the horseradish cream mix the quark and horseradish together and season to taste. Set aside.
To serve slice the fish across the bias. Smear the horseradish cream across one side of individual plates or a large platter. Twirl the fish slices into small ‘cones’ and spread evenly on the cream. Place the different coloured beetroot around the fish, on the cream. Cut the pear into thin ‘matchsticks’ and lean them up against the fish at different angles. Break the kombu into smaller ribbons and drape over the dish. Garnish with the sorrel leaves and serve.