Rub legs well with garlic and sprinkle generously with salt and pepper. Brown the legs in a hot frying pan until brown on both sides. Roast on roasting pan with a rack in a 200C (190F) oven for 35 minutes per kilo (15 minutes per pound).
When the legs are done, remove them from the oven to rest.
For the sauce:
Combine stock and all of the other ingredients, except for the goose fat, in a saucepan and cook until it has reduced by half.
When the goose is ready, remove the excess fat from the pan, reserving 2 tablespoons, and add the remaining liquid to the sauce. Add the 2 tablespoons of goose fat and cook for another couple of minutes.
Reheat the goose legs and serve with a generous amount of sauce on top of the goose.