In a large saucepan, bring white wine to a boil with sugar, salt, white wine vinegar and fish stock. Add bay leaf, thyme and cloves. Finely dice the onion and vegetables, add to the stock and bring to the boil again. Pour the broth over the well boned fillet of catfish and let it simmer on low heat for about 15 minutes. Remove fillet and keep warm. Strain stock (keep vegetables warm), bring to a boil and stir in cold butter, but do not boil again. Season to taste with lemon juice. Arrange vegetable strips on warmed plates, portion Waller, place on vegetables and baste with sauce. Sprinkle with freshly torn horseradish and chopped chives.