In a bowl, combine garlic, ginger, onion, lemon juice, olive oil, cumin, paprika, salt, stock cubes, rosemary, and chili. Use a food processor or blender, to save on time but take care not to process it too much. It should still retain some texture.
Place the meat in a large bowl and toss it with half of the marinade. Set the other marinade aside, to be used in basting the nyama choma.
Use a knife to make slits 2 inches or 5 cm apart on the goat leg and massage the marinade into the meat, making sure to also cover the slits. Cover the meat with aluminum foil and allow to marinate overnight or for at least for 2 hours.
Remove the marinated goat meat from the fridge and allow it to come to room temperature for at least an hour, before setting it on the barbecue. During this time, prepare your grill and set it to high. Cover your grill with ashes if using a charcoal grill, to prevent it from getting too hot.
Grill the meat on high for approximately 3 minutes on each side, or until it attains a proper color then transfer to a triple layer of foil paper.
Place two sprigs of rosemary and the bulb of garlic on top of the goat leg. Cover the meat loosely with foil so it resembles a tent.
Set it on a baking tray or grilling rack, transfer to the barbecue grill then cover the lid, trying to maintain the temperature at medium-low or between 180 and 200 degrees. Grill at medium-low for one and a half hours, turning from time to time.
Once the time is up, mix the honey with 2-3 tablespoons of hot water. Uncover the meat and baste it with the honey glaze. Continue to grill for a further 15-30 minutes or until the desired brownness has been achieved and the juices run clear, or it has an internal temperature of at least 150-160 degrees F.
Once cooked, transfer the meat to a tray and allow it to rest for 10-20 minutes before carving.
Serve nyama choma hot with ugali and kachumbari.