In a large nonstick pot over medium high heat add oil. Once the oil is hot, add the cumin seeds and mustard seeds. After a few seconds add the hing, with green chilis and stir for abou 20-30 seconds.
Add the curry leaves, stir and add the diced onions with a pinch of salt. Lower the heat slightly and cook the onions until they are slightly softened and transluecent (about 6-8 minutes).
Once the onions are soft, slightly increase the heat, add the peas, tomatoes, and ginger and remaining salt. Stir until the ginger is fragrant and tomatoes have cooked down (about 3-4 minutes).
Now, add the cous cous to the pot, give it a quick stir & immediately add the 1 cup of hot water, give it another quick stir to make sure the cous cous and water have mixed and close the lid on the pot quickly. Turn the stove off, move the pot to a different burner and wait for 5 minutes before opening the lid.
After 5 minutes, open the pot and use a fork to gently fluff the cous cous. Taste for salt and add more if necessary. Serve hot and enjoy!