Remove chicken skin if any, then butterfly cut your breast. Hold a long sharp
knife along the thicker part of the breast, place your hand on top and
slice through the breast almost until the end. Cut parallel to your
cutting board, and open the breast like a book. Place cling film on a board, add your breast spread open, sandwich it in cling film and flatten the thicker side using the flat side of a meat mallet or the underside of a
saucepan.