Preheat the oven to 200°C.
Rub a small amount of oil over the bird breasts.
Coat the chopped vegetables in an oiled roasting tin.
Add the birds and giblets to the roasting tin.
Roast for 30 minutes until browned but still slightly pink at the bone.
Joint the cooled birds into legs and wing-breasts and remove the skin.
Crush the carcasses and simmer with vegetables, herbs, wine, and water.
Cook the stock at a gentle simmer for up to 2 hours.
Slit, roast, and peel the chestnuts until charred and tender.
Strain the stock through muslin and reduce by boiling to intensify flavor.
Blend 8 to 12 chestnuts with stock to thicken the sauce and add cream.
Reheat the meat in the sauce while tossing the remaining chestnuts in oil.
Serve the salmi with buttered greens in deep plates.