Heat a wok over high heat. Add the walnuts and cook, stirring constantly, for 2-3 minutes or until hot. Remove and set aside.
Add oil, garlic and chilli to the wok and stir-fry for 30 seconds. Add the mushrooms and stir-fry for 2-3 minutes or until the mushrooms are just tender.
Combine the balsamic vinegar and rice syrup, add to the mushrooms and stir-fry 30 seconds or until well coated.
Remove from the heat, stir in the walnuts and lime juice. Serve with steamed basmati rice.