In a bowl, mix maida, corn flour, rice flour, salt, and pepper powder
Add water little by little to form a smooth, lump-free batter (not too thick)
Add mushroom slices and coat well
Heat oil and deep fry mushrooms in batches till golden and crisp
Drain on a paper towel and keep aside
In a separate pan, heat 1 tsp oil
Add chopped garlic and onions, sauté till onions turn slightly pink
Add green chillies, curry leaves, and salt, mix well
Add red chilli powder and garam masala, stir well
Sprinkle 2 tbsp water if needed to avoid burning
Add soya sauce and mix
Add fried mushrooms and toss till coated evenly
Finish with 1 tsp pepper powder, toss again
Serve hot immediately