Mix together the ginger, chilli and ground spices. Place the goat in a non-metallic bowl, add the spice blend and mix together well. Cover loosely and leave to marinate in the refrigerator for several hours or overnight.
Heat the oil in a flameproof casserole and fry the goat in batches, until deep golden on all sides, lifting out with a slotted spoon on to a plate. Add the onions to the casserole and fry gently for 5 minutes.
Stir in the garlic, stock, coconut milk and tomatoes and bring to a simmer. Return the goat to the casserole, cover and cook in a preheated oven, 150°C (300°F), Gas Mark 2, for 1½ hours or until the goat is tender. Add the potatoes to the casserole and return to the oven for a further 30–40 minutes until tender. Season to taste and serve in bowls.