Grease a baking dish, and place the chicken breasts into the dish. Stir together the honey, Dijon mustard, curry powder, and soy sauce in a bowl until thoroughly combined, and spoon the mixture over the chicken breasts. Cover the dish with foil, and let marinate in refrigerator 6 hours or overnight.
Preheat oven to 350 degrees F (175 degrees C).
Bake the foil-covered dish in the preheated oven for 30 minutes, then uncover, turn the chicken breasts over, and baste the chicken with sauce. Bake an additional 15 minutes, until the juices run clear and the chicken is no longer pink inside. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).
