Peel, wash and chop the sweet potatoes and carrots. Peel and finely chop the onion.
Heat 1 tsp. oil in a large pot. Sauté the onion in it. Add sweet potatoes and carrots. Add 1/2 l water, bring to the boil and stir in the stock. Simmer covered for 15-20 minutes.
In the meantime clean and wash the spring onions and cut them into thin rings. Heat 1 tsp. oil in a frying pan. Fry the minced onions for 3-5 minutes until crumbly. Fry the spring onion briefly. Season with salt and pepper.
Finely puree the soup with a hand blender. Season to taste with salt and pepper. Serve with sour cream and minced meat mixture.