Place the mussels in a large bowl of cold water. Use a small knife to remove any barnacles and pull away the beard. Discard any mussels that are damaged or won’t close when tapped.
Heat the oil in a large saucepan over a medium heat. Add the garlic, ginger and chilli and cook for a couple of minutes. Then stir in the curry powder and cook for another minute. Increase the heat and add in the water and lemon juice. Bring to the boil. Add the mussels and cover tightly. Allow the mussels to cook for 3-4 minutes, shaking the pan from time to time to ensure they cook evenly. Discard any that have not opened.
Stir through the scallions, pak choi and beansprouts. Cook for another couple of minutes, gently stirring, to allow the vegetables to cook. Taste and season with a little black pepper.
Ladle in bowls or soup plates and serve with crusty bread to soak up the juice.