Heat oil in a saucepan and splutter cumin seeds.
Add in the onions and cook till it becomes soft.
Add in the green chilies and ginger paste and saute for a couple of minutes.
Add in the coriander and turmeric powder and saute till the raw smell goes.
Add the chopped tomatoes and chilli powder and cook on low flame with closed lid till the oil floats on the top and the tomatoes are all smashed up.
Add a little water, around 1/2 cup, allow to boil.
Now add in the mushrooms, mix well and cook till the mushrooms are done.
Sprinkle garam masala and adjust the salt. Garnish with curry leaves and serve.