Spread oil on a non-stick pan then heat it.
Add the onions and mushrooms a pinch of salt. Cook until the mushrooms soften a bit on medium flame. Stir occasionally.
Meanwhile in a big bowl beat the eggs, milk, oregano, and sage, salt and pepper, chilli powder until blended.
Spread the mushroom and onion mixture evenly on the pan and add the egg mixture.
Sprinkle the tomatoes, green chillies and the coriander leaves.
Cook on low heat until the eggs are set. (About 10 minutes).
You can try flipping it or stand the eggs covered for another 10 minutes. I have flipped it.
Cut into wedges and serve.