Wash the mushrooms and pat dry. Chop them length-wise into 4 pieces. First cut them into halves, then again cut the halves into 1/4ths.
Mix the cornflour, all-purpose flour, tandoori masala, ginger-garlic paste, pepper powder and salt. Make a thick batter by adding ¼ cup water or as needed. Add water using a tablespoon little by little to make a thick batter. Dip the chopped mushrooms into the batter.
Heat oil in a kadai/wok and deep fry the batter coated mushrooms.
Drain them on a tissue paper.
In another kadai/wok, add 1 tablespoon oil. If some oil remains after deep frying the mushrooms, you can use the same oil.
Fry the curry leaves, chopped coriander leaves and finely chopped green chili for few seconds. Add the fried mushrooms and mix everything.