Step #1 Add 2 tsps of oil & 2 tbsp of broth to a large pot over med-heat/flame.
Step #2 Add the onions, leeks & marjoram & saute for 15 mins, or until vegetables are tender.
Step #3 Add the potatoes & 7 c broth, reduce heat to low, cover & let simmer for 25 mins.
Step #4 Add the buttermilk, ground black pepper & cardamom.
Step #5 Puree the soup with an immersion mixer ot in small batches with a mixer or food processor/blender.
Step #6 While the soup is simmering, place the mushrooms & the remaining tsp of oil & tbsp of broth In a large-ish skillet over med-heat/flame & saute until the liquid evaporates & the mushrooms are golden in color.
Step #7 Spice up with salt & pepper to taste.
Step #8 At the same time boil the sliced carrots & potatoes in a small saucepan.
Step #9 Mix the mushrooms, carrots & potatoes into the pureed soup.