Preheat the oven to 400°F. Coat a shallow roasting pan with cooking spray.
Using a sharp paring knife, slice a pocket into each chicken breast, as if halving a bagel, without completely cutting through the other side. Arrange chicken in prepared pan and set aside.
In medium bowl, combine blue cheese, almonds, apple, and dill. Add a pinch each of salt and black pepper. Mix together with a fork until mixture is well blended and comes together. Divide mixture into four equal portions and spoon each portion into the pocket of the chicken. Brush olive oil all over the top of chicken and season the top with salt, black pepper and dried onion (1 teaspoon dried onion for each breast). Bake 25 to 30 minutes, until chicken is golden brown and cooked through.
Nutrition information per serving for 4 servings:
Calories 490 kcals, Cholesterol 141 mg, Total fat 25.5 g, Fiber 3.1 g, Saturated 7.9 g, Calcium 217 mg, Monounsaturated 12.1 g, Magnesium 94 mg, Polyunsaturated 3.7 g, Sodium 867 mg, Carb 11 g, Potassium 624 mg, Protein 53 g, Vitamin E 5.2 mg