Melt 2 tablespoons butter in a skillet and add chopped onion. Cook, stirring, until soft and tender. Stir in apple and cook for 3 minutes. Stir in raisins, parsley and mix. Add bread crumbs and mix until all ingredients get together. Set aside.
Place breasts fillet on a table and insert a knife in the middle of 1 side of chicken breast through the center. Move knife back and forth in order to create a pocket. Do the same with remaining chicken breast halves. Stuff chicken with the apple mixture and close with a toothpick.
Heat oil in a skillet and sear stuffed chicken breasts on both sides. Transfer chicken to a baking dish and bake in preheated oven to 425ºF (220ºC) for 15 minutes or until tender and juicy.
Discard oil from skillet and melt remaining butter. Remove from heat. Add flour stirring quickly to prevent lumps. Gradually stir in apple juice and chicken stock until combined. Bring sauce to a boil over medium heat until thick and creamy.
Remove chicken breasts from the oven and cool for 3 minutes. Cut each chicken breast into 3 diagonal slices. Serve chicken with apple sauce and Rice with Creamy Leek.