Wash and peel the sweet potatoes, cut into large pieces and cook in salted water for about 20 to 25 minutes. Then drain and allow to evaporate.
In the meantime, peel the apples, remove the core and chop the flesh. Heat the butter. Steam the apple pieces in it. Add the apples with the butter to the sweet potatoes. Puree with the potato masher. Gradually add the heated milk. Season with salt, pepper and nutmeg and serve sprinkled with pecans.