Add 2 teaspoons of
oil and 2 tablespoon of broth to a large pot over medium heat. Add the
onions, leeks and marjoram and saute for 15 minutes, or until vegetables
are tender.
Add the potatoes and 7 cups broth, reduce heat to low, cover and simmer
for 25 minutes.
Add the buttermilk,
ground black pepper and cardamom. Puree the soup with an immersion blender
ot in small batches with a blender or food processor.
While the soup is simmering, place the mushrooms and the remaining teaspoon
of oil and tablespoon of broth in a large skillet over medium heat and
saute until the liquid evaporates and the mushrooms are golden in color.
Season with salt and fresh ground black pepper to taste.
At the same time boil
the diced carrots and potatoes in a small saucepan.
Mix the mushrooms, carrots and potatoes into the pureed soup. Serve immediately.