Wash the leeks and cut them into slices. Peel and cut the potatoes into small cubes, and finely mince 2 cloves of garlic.
In a large saucepan, heat olive oil and butter. Add the minced garlic and cook for about 30 seconds. Then add the leeks and cook for about 5 minutes while occasionally stirring. Once they are soft, you can set aside some pieces of leek for garnishing. If the leeks start sticking to the bottom of the pan, you can add a splash of water.
Add the potatoes and vegetable broth to the pot. Then add nutmeg, salt, and pepper. Put the cover on and let simmer for 15 minutes or until the potatoes are tender.
Blend the soup until smooth. If it is too thick, you can add a bit of water and blend again. Your soup is now ready to serve. Garnish with the leek that you saved, a light sprinkle of nutmeg, and some olive oil.
Notes
For a vegan version, skip the butter and instead add another tbsp of olive oil.
You can also enjoy this soup not blended. In that case, cut the potatoes and the leeks in bite sized pieces.