In a large pot, bring chicken broth, coconut milk, kaffir lime leaves, cayenne peppers, ginger, red curry paste, lime juice, sugar and salt to a boil. Reduce and let simmer for 10 minutes.
While curry is simmering, mix salt, black pepper, and lime juice together. Coat salmon fillets in mixture. Heat vegetable oil in a pan and sear marinated salmon for 2-3 minutes on each side.
Remove kaffir lime leaves and add bok choy into curry broth 1-2 minutes prior to serving. Pour creamy curry broth over salmon and garnish with fresh chopped green onions.