Peel, wash and chop the potatoes. Cook in little boiling salted water for about 15 minutes. In the meantime peel onion and garlic. Finely dice the onion, press the garlic through a garlic press. Briefly bring the stock, vinegar, onion, garlic and herbs to the boil.
Drain the potatoes and mash them finely. First stir in the warm stock, then the sour cream. Season to taste with salt and pepper. Let it cool down, put it in a bowl and garnish with basil