Melt the butter in a heavy 4-quart saucepan or pot, and add the celery and onion. Sauté over medium-high heat until the celery wilts and the onions are translucent but not brown. Lower the heat and add the curry powder. Cook for 5 minutes, stirring occasionally.

Add the broth and apples. Partially cover, and simmer over medium-low heat for 35 to 40 minutes, or until all the vegetables are very soft.

Strain the broth and degrease if necessary. Reserve the vegetables. Add a little broth to a blender, then add a portion of the vegetables. Puree the vegetables until they are very smooth. Repeat, until all the vegetables are pureed.

Combine the strained broth and puree, stirring to blend well. Return the soup to a saucepan, add the chicken, and slowly reheat. Ladle into bowls and garnish with chives.

To serve cold, chill the soup and chicken in the refrigerator for several hours and mix in the chicken just before serving.