Place curry powder in a large skillet and stir over medium heat until slightly darker in color (about 3 minutes). Add chopped apple, onion, lemon juice, mushrooms, broth, and 1 1/2 C. of the apple juice; bring to a boil.
Rinse chicken and pat dry; add to skillet. Reduce heat, cover, and simmer for 30 to 40 minutes, or until meat near bone is no longer pink; cut to test. Lift chicken from pan; arrange on a warm platter. Keep warm.
In a 1 cup measure, blend flour with remaining 1/2 C. apple juice. Gradually add to sauce in pan, stirring; increase heat to high and cook, stirring until sauce is thickened. Pour over chicken. Serves 4 to 6.