In a pan dry roast the vermicelli till light brown in color. If you are using vermicelli that has already been roasted, then there is no need for roasting. Keep the vermicelli aside.
Finely slice the onion, green chili, ginger and coriander leaves.
In the same pan/kadai heat oil or ghee and add the mustard seeds and let them pop in the oil.
Now add the urad dal and when they turn golden brown in color add the onions, curry leaves, ginger, green chili and sauté till they become translucent.