For 8 ounces cooked chicken breast, start with 10 ounces boneless skinless chicken breast halves. Lightly coat an unheated panini griddle, covered indoor electric grill, or large nonstick skillet with cooking spray. Preheat over medium heat or according to manufacturer's directions. Add chicken. If using griddle or grill, close lid and grill 6 to 7 minutes or until done (165°F). (If using skillet, cook chicken 10 to 12 minutes or until done, turning once.) Cool chicken slightly; thinly slice crosswise.