Remove the legs, wings and breast meat from the chicken. Place the chicken carcass in a roasting tin and roast for 30–40 minutes, or until golden brown. Transfer the carcass to a large pot.
Add 1 onion, the carrot, celery and 1 bouquet garni. Cover with cold water and simmer for 35–40 minutes. Strain, discarding the vegetables and bones.
Season the chicken pieces with salt and black pepper. Heat the butter and oil in a large casserole. Add the chicken and fry until the skin is evenly browned. Meanwhile, blitz the remaining onion and the garlic cloves in a food processor until finely chopped. Remove the chicken from the casserole, add the onion and garlic, along with the bacon, and fry until soft and brown.
Turn the heat up and deglaze the casserole with a good splash of red wine. Return the chicken legs and wings to the pot.
Pour in the remaining red wine and 150ml of stock. Add the remaining bouquet garni.
Cook over a low heat for 1 hour, topping up the liquid if necessary with stock. Add the chicken breasts and cook for a further 20 minutes or until the chicken is cooked.
Stir in the cacao to finish and serve with mashed potato.