Remove the cooked bird from the oven. Set bird aside to rest, skim excess fat off the juices in the roasting pan, then add the onions and cumin seeds.
Fry gently until the onions are tender. Add the cocoa powder, honey and enough flour to absorb the juices and remaining fat. Cook for 1-2 minutes. Gradually stir in the wine and stock and bring to a simmer. Adjust seasoning to taste, cook gravy for 5-10 minutes, then serve with the turkey.
It may sound unusual, but adding cocoa to the chunky onion gravy really works, offsetting the tangy wine.