Crack the eggs in a bowl, and add milk. Season with salt, and red chili powder. Whisk. Add capsicum and coriander. Mix and set aside.
Heat 1 tablespoon oil. Add mushrooms cook on medium heat for 2-3 minutes, until they start to soften and turn golden. Season with salt and black pepper, and remove in a plate. Set aside.
In the same pan, add another tablespoon of oil.
Add the whisked eggs, and tilt the pan to spread the eggs evenly the surface. Cook the omelet, and about every 30 seconds, lift the edges of the omelet with a spatula and let the liquid eggs run underneath. Basically, the eggs will start setting in the centre, and once the pan is tilted the runny eggs will have a chance to get set as well.
Once the eggs are almost set, spread the mushrooms in the middle along with the grated cheese. Use the spatula to fold the omelet in half over itself.
Let it cook for another minute so the cheese is completely melted, and the eggs are set.
Remove on a plate, and garnish with coriander and red chili flakes.