Place the chicken pieces in a large bowl with the wine, garlic, herbs, and celery. Marinate in the refrigerator for a few hours or overnight.

To remove the skins from the onions, blanch them in boiling water for 1 minute, then refresh in cold water. Trim the roots, then peel.

Put half the butter into a large, heavy saucepan and brown the onions, bacon, and mushrooms. Remove and reserve.

Remove the chicken from the marinade, reserving the marinade. Strain to remove the flavourings. Pat the chicken dry and season with salt and pepper.

Add the remaining butter to the pan and brown the chicken on the skin side over a medium-low heat. Tip off all the fat and reserve.

Return the vegetables and bacon pieces to the pan and add the marinade and enough stock nearly to cover the chicken pieces.

Cover with a tightly fitting lid and simmer slowly for about 45 minutes, until the onions and chicken are tender. Test for doneness by piercing a chicken thigh with a skewer which should glide easily into the flesh.

Lift out the chicken, vegetables and bacon and put them on to a warmed serving dish. Keep warm while you make the sauce.

Allow the sauce in the pan to cool a little.

Mix the flour with enough of the reserved butter to make a paste.

Whisk this into the wine sauce in the pan, while bringing slowly back to the boil.

Boil for 2 minutes. Adjust the thickness of the sauce to coating consistency either by boiling further or by adding water, as required. Taste and adjust the seasoning.

Taste the sauce. Add salt and pepper to taste and spoon it over the chicken. Garnish with parsley.