Layer broccolini, snow peas, baby buk choy and red chilli in a large baking-paper-lined bamboo steamer. Steam, covered, over a large wok of simmering water about 5 minutes or until vegetables are just tender.
Combine vegetables, char siu sauce and sesame oil in a large bowl. Heat peanut oil in a small saucepan until hot; pour oil over vegetable mixture then toss to combine. Serve sprinkled with toasted sesame seeds.