Preheat the oven to 160 ° C / 140 ° C hot air / gas 3.
Place the bacon in a large nonstick ovenproof skillet or explosion-proof casserole dish and fry over medium heat for a few minutes to release the fat. Add the onions and continue to fry until the bacon is brown around the edges. Transfer the bacon and onions to a plate using a skimmer and set aside.
Lightly season the chicken. Put the oil in the unwashed dish, add the chicken and brown over high heat, turning once. Transfer to the plate with the bacon and onions.
Distribute the flour in the dish (adding a little more oil, if necessary) and stir to combine. Gradually add the hot broth while whisking and allow to thicken. Pour in the wine and return the bacon, onions and chicken to the pan. Mix well, add the thyme sprigs, sage sprigs and bay leaves. The sauce will be quite thick at this point. Bring to a boil, season well with salt and black pepper and cover. Transfer to the oven for 30 minutes.
Take the dish out of the oven and add the mushrooms and crème fraîche. Mix well and return to the oven, 15 to 20 minutes more, until the chicken is tender.
Meanwhile, heat the butter in a small skillet over medium heat. Add whole sage leaves and fry until crispy.
Remove the bay leaves, thyme and sage sprigs from the casserole dish and throw them away (some leaves will have fallen to flavor the casserole dish). Stir in the parsley and serve with the crispy sage leaves on top.
Can be prepared up to a day in advance. Add the crème fraîche and mushrooms when reheating.
From Love to Cook by Mary Berry published by BBC Books