Preheat the slow cooker if necessary; see the manufacturer's instructions. Make the dumplings. Put half of the spring onions into a food processor with the coriander and ginger and chop finely. Add the cod, cornflour and egg white and process until the fish is finely chopped. With wetted hands, shape the mixture into 12 balls.
Pour the boiling fish stock into the slow cooker pot, add the fish sauce, curry paste and soy sauce. Add the rest of the spring onions, the carrot and garlic and drop in the dumplings. Cover with the lid and cook on low for 2–3 hours.
When almost ready to serve, add the asparagus and pak choi to the broth. Replace the lid and cook on high for 15 minutes or until just tender. Ladle into bowls and serve.