Clean, wash and finely dice the carrot and celery. Peel and dice the onion. Heat the fat in a pot and lightly fry the vegetables in it. Dust with flour and curry, briefly sauté and deglaze with stock and cream.
Let the soup simmer for about 10 minutes, stirring occasionally. Meanwhile wash the apple, quarter it and remove the core. Halve the apple quarters again and cut into thin slices. Puree the soup finely.
Add apple and raisins and bring to the boil briefly. Season to taste with lemon juice, curry and salt. Arrange on 4 deep plates and serve sprinkled with lemon balm as desired.