Carefully butterfly the chicken breasts and spread two tablespoons of pesto on one side. Top with a handful of grated mozzarella and then fold back over again.
Lay four pieces of bacon in an "X" shape, two on each line. Put the chicken breast in the middle and wrap the bacon around them. Repeat for the other two chicken breasts. Lay on a sheet lined with baking paper and bake for 35/40 minutes or until the chicken is cooked through.