Peel the sweet potatoes and the onion and cut into cubes. Cut the leek into rings and wash well.
Heat the oil in a pan with a lid and fry the onion cubes, add the vegetables and sweet potatoes and season. Cook over low heat with the lid closed until the vegetables are cooked (approx. 10 to 15 minutes). Add sour cream and finely chopped herbs and season with salt, pepper and ginger. Serve garnished with chives.