Peel and dice the potatoes, onion and garlic. Fry the bacon in a pan until crispy, then remove it and set aside.
Add a little butter to the bacon fat and sauté potatoes and onions in it. Sauté the garlic briefly, then deglaze with the stock and milk, bring to the boil and cook the potatoes for about 20 minutes. Puree the soup in the mixer or with the hand blender until smooth. Melt half of the cheddar in the soup, stir in the sour cream and season the soup to taste.
Serve the soup garnished with bacon, remaining cheese and cress.
Note: Since the potatoes contain and bind differently in terms of starch, it is advisable not to add all of the liquid right away.