Rinse the fish with cold water, pat dry, cut into cubes and drizzle with lemon juice. Finely slice the cabbage. Fry the cabbage in 30 g of the butter until golden brown and remove from the pan. In the meantime, cut the boiled potatoes into thick slices, fry both sides in 30 g butter and add the cabbage. Fry the fish cubes in a coconut oil and butter mixture. The fat must be very hot, otherwise the fish will draw water and disintegrate. Season the cabbage to taste and distribute the fish cubes on top. Boil the roast set from the fish with the vegetable stock, stir in the creme fraîche and pour over the fish pan, sprinkle with parsley and serve.