Preheat the oven to 200°C. Place a wire rack in the bottom of a roasting dish. Place the Sadia Chicken Breasts, skin side down on a board. Using a small sharp knife, carefully cut away the ribcage and breast bone from the breast, taking care not to tear the skin. Remove and discard.
Heat one tablespoon of olive oil in a frying pan over medium heat. Add the onion and cook, stirring occasionally, for 5 minutes or until softened. Remove from the heat. In a large bowl, combine the onion, breadcrumbs, dates, walnuts and sage and mix well.
Place the breasts skin-side down on a clean board, and then open the tenderloin so the breast lies flat. Spoon the stuffing down the centre of each breast and fold in the sides to enclose. Using kitchen string, tie at 2 cm intervals to secure.
Place the breasts on the wire rack and brush with the remaining olive oil. Pour the stock into the pan and cook, basting occasionally for 35-40 minutes or until cooked through.
Remove from the oven, cover with foil and set aside for 10 minutes to rest before slicing and serving. Reduce the pan juices to serve with the sliced chicken accompanied by vegetables of your choice.