Heat the oven to 425 F. Lightly coat a baking dish with cooking spray. In a small bowl, add the raisins and cover with warm water. Set aside and allow the raisins to swell.
Spray a large skillet with cooking spray. Add the onions, celery, garlic and bay leaf. Saute until the onions are translucent, about 5 minutes. Remove the bay leaf and add the apples. Cook for another 2 minutes, stirring occasionally.
Drain the raisins and pat with paper towels to remove the excess water. Add the raisins to the apple mixture. Stir in the water chestnuts and remove from heat. Let cool.
Loosen the skin on the chicken breasts. Place the apple-raisin mixture between the skin and breast. In another skillet, heat the olive oil over medium heat. Add the chicken breasts and cook until browned, about 5 minutes on each side.
Transfer the chicken breasts to the prepared baking dish. Cover and bake until a meat thermometer registers 165 F, or about 15 minutes. Remove from the oven.
While the chicken is baking, in a saucepan over low heat, heat the milk, curry powder and flour. Stir until the mixture thickens, about 5 minutes. Pour the mixture over the chicken breasts. Cover and return the chicken to the oven and bake another 10 minutes.
Transfer the chicken breasts to warmed individual plates. Spoon the sauce from the pan over the chicken and garnish with lemon wedges.