Cut 2 slashes an inch apart across the width of each chicken breast. Place chicken in a large bowl or large plastic zip-loc bag. Add agave, sesame oil, and soy sauce. Add a large pinch of salt and black pepper. Toss well until chicken is coated. Refrigerate 8 hours.

Preheat oven to 450°F. Pour marinade into a saucepan and set aside. Place chicken on a rimmed metal baking sheet lined with aluminum foil. Bake 20 to 25 minutes until chicken is just firm to touch. Before serving, bring marinade to a brisk boil for one minute. Drizzle marinade over chicken and serve.