Heat large heavy based frying pan and fry the bacon until lightly golden, remove from the pan and set aside. Add the apple slices and cook for 2-3 minutes over a medium heat, set aside with the bacon.
Heat 2 tbsp oil in the pan. Toss the liver in the flour, shaking off any excess and cook for 3 minutes on each side, until lightly golden. Remove with a slotted spoon.
Add the apple juice to the pan, bring up to the boil and allow to reduce by half. Reduce the heat, add the mustard, cream and sage and allow to simmer gently for 2-3 minutes or until the sauce has reduced by half.
Return the liver, bacon and apple slices to the pan. Season to taste, heat through and serve.