Combine batter ingredients well in a mixing bowl. Dip mushrooms in batter and deep-fry in hot oil until golden brown. Dish out and drain on absorbent paper.
Heat margarine in a clean wok over medium heat until melted.
Stir-fry curry leaves and bird's eye chillies until fragrant.
Add oats and seasoning. Stir-fry briskly then add fried mushrooms.
Toss and fry over high heat until oats are crispy.
Dish out and serve immediately.