3 tablespoon sour cream
In a deep saucepan, heat the butter over medium heat. Add the bacon and 2 tablespoons of rosemary and fry for a few minutes until fragrant. Add the chopped onion and fry until golden. Peel the potatoes and chop them into chunks. Add them to the bacon onion mixture in the pan, fry for another minute while stirring constantly. Add the stock, bring to a boil. Cover the saucepan and let simmer for about 20 minutes or until potatoes are cooked. Take off the heat and let cool a little.
Puree the soup in a food processor. Transfer back to the pan, heat up if necessary and stir in 2 tablespoon of sour cream. Transfer to serving bowls. Decorate each bowl with a few drops of sour cream and chopped rosemary.
Serve with fresh bread to dip into.