Peel and chop the onion and garlic. Heat the fat in a saucepan. Sauté onion and garlic. Deglaze with tomato juice and 1/4 l water and bring to the boil. Stir in stock, season. Let simmer for about 5 minutes
Stir starch and 2 tablespoons of water until smooth. Stir into the soup, bring to the boil again. Season to taste with salt, paprika and sugar
Heat the meatballs in the soup. Wash the basil and cut the leaves into strips, except for some for garnishing. Add to the soup
Arrange the soup on plates. Stir sour cream or sour cream until smooth and put a blob on each. Garnish with remaining basil