Heat the groundnut oil in a large casserole dish over a moderate heat until hot. Add the carrot, baby sweet corn, onion and yellow pepper and sauté for 2-3 minutes, stirring occasionally. Add the kaffir lime leaves, Thai peas and vegetable stock and bring to a simmer.
Stir in the coconut milk, return to a simmer and cook gently for 10-15 minutes until the vegetables are soft. Season to taste with the fish sauce and lime juice, then stir in the mangetout.
Spoon into serving bowls and garnish with the lime leaves. Serve immediately.