Peel and finely chop the onions. Peel the garlic and press it through a garlic press. Heat the lard. Fry onions and garlic in it until transparent. Add curry and sauté briefly. Deglaze with broth.
Wash the lentils, add to the stock, bring to the boil briefly. Cover and cook over medium heat for about 45 minutes. In the meantime, wash, clean and quarter the tomatoes. Remove seeds with a spoon.
Cut the fruit flesh into very small cubes. Peel the mango, cut the flesh from the core and dice finely. Add tomato and mango cubes to the soup 5 minutes before the end of the cooking time. Season to taste with salt, pepper and lemon juice.
Serve sprinkled with mint leaves.