Heat oil, add chopped mushroom and onion
Saute until mushroom starts browning. Add garlic, green chillies, saute for few seconds
Add veg stock to mushrooms, salt and pepper. Mix well
Add 5tbsp water to corn flour. Make a slurry. Add to mushrooms. Simmer and cook on low flame until gravy starts thickening. Do stir in between.
Serve hot with bread, loaf or rotis