Preheat the oven to 160°C/140°C fan/Gas 3.

Fry the bacon on medium heat for a few minutes in a large non-stick frying pan or casserole, to remove the fat.

Add the onions and keep frying until the bacon becomes brown at the edges.

Transfer the bacon and onions to a plate using a slotted spoon and keep them aside.

Lightly season the chicken and add oil to the same dish.

Place the chicken in the dish and cook on high heat, turning once, until it becomes brown.

Transfer the chicken to the plate with the bacon and onions.

Add flour to the same dish, stirring it along with a little more oil if required.

Gradually add the hot stock and whisk until the mixture thickens.

Pour in the wine and add the bacon, onions, and chicken to the dish.

Add thyme, sage, and bay leaves, stirring well.

Stir till the sauce gets thick.

Season the chicken casserole with salt and black pepper and cover it.

Transfer it to the oven and bake for 30 minutes.

Take out the dish from the oven and add mushrooms and crème fraîche.

Mix well and return it to the oven.

Bake for another 15-20 minutes, until the chicken becomes tender.

Heat butter over medium heat in a small pan.

Add whole sage leaves and fry until they become crisp.

Remove the bay leaves, thyme, and sage sprigs from the casserole and discard them. Some leaves would have already fallen off to flavour the casserole.

Stir in the parsley and serve it with the crisp sage leaves on top.