Heat a wok over high heat until hot. Add oil, garlic and mushrooms and cook, tossing frequently, for 3 - 4 minutes or until golden and just tender. Remove to a plate. Reduce heat to medium, add satay sauce and coconut milk and cook, stirring constantly, for 2 minutes or until sauce comes to the boil.
Add mushrooms and cook, tossing constantly, for 2 - 3 minutes or until mushrooms are tender. Remove from heat, stir through green onions and peanuts, and serve.