Melt the butter in a sucepan and add the onion, garlic, celery and apple. Cook, stirring often, for about 5 minutes. Blend the flour, curry powder and mustard and sprinkle it over the vegetables, stirring. Add the bay leaf. Add the chicken broth, stirring rapidly with a wire whisk. When the mixtures has thickened, le it simmer for 15 minutes. Stir often from the bottom to prevent sticking. Add meat, milk and finely chopped chutney and simmer for 4 or 5 minutes longer. Serve with rice.