1. Make Strawberry Dressing by mixing apple juice, strawberry jam, and vinegar until blended.
2. Remove fat from chicken. Spray 8 or 10 inch skillet with cooking spray; heat over medium-high heat. Cook chicken in skillet 15-20 minutes, turning once, until juice of chicken is no longer pink when centers of thickest pieces are cut. Remove chicken to cutting board. Add dressing to skillet; stir to loosen any pan drippings.
3. Slice chicken. Arrange spinach on serving plates. Top with chicken, strawberries, and cheese. Drizzle with dressing. Sprinkle with walnuts.