Combine the garlic and spices. Melt the butter in a large heavy frying pan over a medium-high heat. Add the chicken and sauté until lightly browned on all sides. Transfer the chicken to a casserole dish.
Drain all but 1 tablespoon of the fat from the frying pan. Add the celery, onion, carrot, leek and spice mixture, and blend well until the spices are aromatic.
Add a small ladle of stock and cook over a low heat, stirring constantly, until the vegetables are tender. Add to the chicken
Stir the remaining stock into the casserole dish, and season with salt and pepper. Cover and simmer for 30 minutes.
Remove the chicken with a slotted spoon and set aside. Add the rice to the soup and continue cooking for a further 15 minutes.
When the chicken is cool enough to handle, cut into bite-sized pieces, discarding the skin and bones. Return the chicken to the soup. Peel, core and dice the apples, and blend into the soup with the yogurt. Simmer for 10 minutes.
Stir in the lemon juice, then blend in the cream. Taste and adjust the seasoning if necessary. Serve hot.