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 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.