Combine the fish stock, coconut milk, Madras curry powder, ground cumin, chilli powder and sugar in a large saucepan. Bring to a simmer and add the salmon.
Simmer for 8-10 minutes over a gentle heat then add the mussels and mangetout and simmer for a few more minutes until the mussels are heated through. Spoon into serving bowls and garnish with the Maldon salt before serving.
*costing based on using leftovers.