Boil peeled, diced potatoes with milk, water, soup cubes and herbs until soft and then puree, season with salt.
Place the fish on aluminum foil, season with salt, pepper, cover with lemon wedges, place the juniper berries and butter flakes on top, close the foil very well and place in a pan with water and let it simmer for about 15 minutes.
Take the fish out of the foil, tear into small pieces and add to the soup with the fish stock, bring to the boil briefly, stir in the creme fraiche and let it steep for about 3 minutes.