1. For the Blue cheese dressing, combine blue cheese, mayonnaise, sour cream, milk, and fresh lemon juice in small bowl. Set aside.
2. Combine flour, salt, pepper, and ground red pepper in a pie plate. Coat both sides of chicken in flour mixture, shaking off excess.
3. Heat oil in 12-inch nonstick skillet. Stir in hot pepper sauce. Add chicken and cook 6 to 8 minutes per side, until browned. Transfer to cutting board; cover loosely and let stand 5 minutes.
4. Meanwhile, separate ribs from celery; peel the outside ribs. Slice diagonally into 1/2-inch-thick pieces. Combine in medium bowl with lettuce and apples.
5. Slice chicken into 1/2-inch-thick strips; add to salad, then toss with Blue Cheese Dressing. Makes 6 servings.