Fill the base of your steamer with water and bring to the boil. Drain the tofu and place it on a heatproof plate that will fit inside the steamer. Steam the tofu for 15 minutes, then drain off the excess water and carefully transfer to a serving plate.
Heat the soy sauce, sesame oil and oyster sauce together in a small pan until hot. Pour the mixture over the tofu, scatter with the red chilli, spring onion and coriander leaves and serve with steamed rice alongside.