In a large sauce pot, over medium heat add bacon, and fry until cooked and crispy. Remove bacon and set aside. Then add leeks and sauté for about 8 minutes until the leeks are tender. If the leeks start to brown, reduce heat. Then add garlic and sauté for about 30 seconds.
Add broth, potatoes, salt and pepper (add dried herb now if using), then reduce heat. Simmer for about 20 minutes until the potatoes tender.
Using a hand blender or food processor/blender, puree soup until smooth and no chucks are remaining. If using a blender, adjust the amount of soup you add, to avoid the hot soup splashing up on you, and hold a tea towel over the opening while the steam is escaping.
In a small bowl, add the sour cream/greek yogurt and add a couple lades of the soup and mix well with a fork or whisk until the sour cream is blended well. Pour the sour cream mixture into the hot puree soup and whisk until well blended. Add the chopped dill, thyme or rosemary and taste if more seasoning is needed.
Ladle into bowls and garnish with fresh dill, thyme or rosemary and bacon.
