Flatten chicken to 1/4 inch thickness; sprinkle both sides with salt and pepper. In a large non-stick skillet, brown chicken in olive oil and 2 teaspoons butter over medium heat for up to 10 minutes on each side or it is no longer pink inside.

Remove chicken to a plate and cover with aluminum foil to keep warm. In the same skillet, whisk the lemon juice, parsley and mustard until blended. Whisk in broth; heat through. Place each chicken breast on a plate, spoon sauce over chicken and sprinkle some chopped green onions on top.