Peel and wash the potatoes and carrots. Roughly dice potatoes and put them in cold water. Clean and wash the celery and leek. Cut carrots, celery and leek into slices. Wash fish, dab dry and cut into coarse cubes.
Mix with lemon juice and chill. Lightly salt fish stock, white wine and 400 ml water and bring to the boil. Add drained potato cubes and cook for 5 minutes. Add carrots and cook for 3 minutes.
Bring the remaining ingredients to the boil and let them simmer for another 4 minutes at medium heat. Season to taste with salt and pepper. Serve the soup and garnish with fresh parsley as desired.