Flatten the chicken breasts slightly and dust with the flour.
Heat the oil and butter in a large, wide pan with a lid, add the chicken, then sauté on all sides until slightly browned.
Add the shallots, then sauté for about 2 mins until they start to soften, but not colour.
Pour in the brandy, carefully ignite, then stand well back until the flames have died down.
Stir in the stock and bring to the boil.
Reduce heat, cover the pan, then cook for 15 mins until the chicken is tender.
Add the asparagus (optional) or sliced mushrooms to the sauce.
Cover, then cook for 5 mins more until tender.