Season fish on both sides with remaining 1/4 tsp salt and 1/4 tsp pepper.
Add fish and peas to pan and keep gentle simmer, lowering heat if necessary. Cover and cook for 5 minutes, turning fish after 3 minutes. Uncover and cook 2 to 3 minutes more, or until fish flakes when prodded gently with fork.
To serve, spoon broth and vegetables into wide soup bowls and place piece of fish in centre. Top with more broth.