Peel and dice potatoes of about 2cm in thickness. Chop onion and cut finely. Heat butter in a pot and steam onions until translucent. Add potatoes and sautée some minutes. Add white wine, stock, cloves and cook covered approx.15 minutes. Add diced zucchini and cook over low heat approx 15 minutes. Cut fish fillets into cubes and add them for the last 5 minutes uncovered. Add cream fraiche to make the juice creamy. Season to taste with salt, pepper and dill.