Let's start with the sauce. Thinly slice the shallot and brown it in a saucepan with the butter. Pour the cider and let it reduce for 10 minutes over medium heat. Incorporate the cream and season to taste. Let reduce again for 10 min. You must obtain a homogeneous mixture. Keep warm.
Meanwhile, split the meat of the duck breasts diagonally. In a non-stick frying pan, heat the skin side without adding fat. Leave to brown for 5 minutes. Cover and continue cooking over low heat for another 10 minutes. 1 min before the end of the cooking time, turn them over on the flesh side. Set aside.
Peel the apples and cut them into quarters. Place them in a bowl of water with lemon juice. Remove the fat from the pan, drain the apples, and fry them in the pan for 5 minutes. Turn them regularly so that they do not stick. Keep warm.
Cut the duck breasts into slices and arrange them in a serving dish. Place the apples and coat the whole with cider sauce.