Soak the toast in cold water. Roast sesame seeds in a pan without fat, take them out and put them in a bowl. Wash the coriander, shake dry and put 1 stalk aside. Finely chop the top 1/3 of the remaining coriander stems. Knead minced, squeezed toast slices, mustard, egg, curry, cumin and 1/2 of the coriander, season with salt and pepper. Shape the chopped mass into small balls
Cut the lemongrass into pieces. Heat the oil in a pan. Add lemongrass to the oil to flavour it. Fry the meatballs in the hot oil for about 10 minutes while turning. Remove pieces of lemongrass from the oil if they become too dark
Mix yoghurt, remaining coriander and sour cream. Stir in chili sauce, season with salt and pepper. Sprinkle meatballs with sesame seeds and arrange on a plate. Garnish the dip with coriander and serve with the meatballs