Sauti garlic, onion and ginger in oil. Add two cups thin coconut milk and lemon grass. Bring to the boil Add prawns, cover and simmer for 10 minutes. Remove prawns. Add thick coconut milk, reduce heat, stir constantly. Add buko meat and chili peppers. Simmer for about 3 minutes, return prawns and allow to boil for two minutes. Discard lemon grass. Season with patis and pepper to taste.