To make the sauce, heat a little vegetable oil in a thick-bottomed frying pan and brown the vegetables and chicken bones, stirring occasionally. Dust with flour and stir well.
Slowly add the red wine and chicken stock, then the thyme, bay leaf, garlic and tomato purée. Bring to the boil, skim and simmer gently for one hour, topping up with some water if necessary.
Strain the sauce through a fine meshed sieve, then reduce by boiling rapidly until it has thickened to a gravy-like consistency.