Make the marinade. Mix the garlic and ginger with the soy sauce, mirin, sweet chilli sauce and oil. Add the star anise. Put the tofu in a non-metallic dish, pour over the marinade, cover and refrigerate for at least 2 hours or overnight if possible.
Cut the mushrooms into bite-sized pieces and sauté in a hot saucepan for 1 minute. Cut the marinated tofu into 2 cm (¾ inch) squares, mix with the mushrooms and pour over the remaining marinade. Garnish with finely sliced spring onions and sesame seeds and serve immediately.