1 Trim leeks and cut lengthwise. Rinse thoroughly under running water, shake dry and cut into finger-thick rings.
2 Rinse potatoes, peel and cut into 1 1/2 inch cubes.
3 Heat the oil with fennel seeds in a pot. Sauté leeks, add potatoes and pour in 400 ml (approximately 1 3/4 cups) of water. Season with salt and pepper and bring to a boil. Cover and cook over medium heat until tender, about 20 minutes.
4 Meanwhile, rinse basil, shake dry, pluck leaves and cut into fine strips.
5 Rinse salmon, pat dry with paper towels and cut into 2 cm (approximately 3/4 inch) cubes.
6 Puree potato-leek mixture with an immersion blender and stir in the milk. Grate in some nutmeg. Dilute the soup with a little water as desired.
7 Put salmon in the soup and let simmer over medium heat for about 3 minutes. Stir in basil, season soup again and serve.