Slice the chicken breasts into fingers. Thinly slice the apples.

Heat a large nonstick skillet to medium. Sprinkle chicken with salt. Melt the butter in the saucepan. Add the chicken and cook for 4-6 minutes on each side, or until no longer pink. Remove from pan.

Add the apples, brown sugar, and mustard to the pan. Toss to combine. Cook, covered, over medium heat for 3-4 minutes or until the apples are tender. Stir in the chicken and heat until internal temperature reaches 160-165 degrees F.