Preheat slow-cooker, if required. Heat oil in large flameproof casserole over medium heat. Add chicken and cook for about 10 minutes. Remove and set aside. Stir in curry paste and cook for a minute. Pour in soy sauce, coconut milk, fish sauce and stock and bring to boil. Transfer to slow cooker, add chicken, mushrooms and spring onions and season with salt and pepper. Cover with lid and cook on low for 6 - 8 hours or high for 3 - 4 hours. Serve with noodles or rice.