Place a medium pan over medium-high heat and add the oil.
Once hot, add the chopped onions and sauté for 6–7 minutes, until they begin to brown.
Add the finely chopped garlic, ginger, and green chilies.
Stir continuously for 2–3 minutes until fragrant.
Remove the pan from the heat and stir in the ground coriander, turmeric, and chili powder. Return the pan to the heat and stir for one minute to toast the spices.
Add the mung bean sprouts, 4 tablespoons (60 ml / 2 fl oz) of water, and the salt.
Stir well to combine, ensuring you scrape the bottom of the pan.
Reduce the heat to very low and cover the pan.
Cook for about 20 minutes, or until the sprouts are tender. See for the traditional Bombay cooking method using a special lid.
Once cooked, transfer the sprouts to a serving dish.
Garnish with fresh diced tomatoes and chopped cilantro just before serving.
Adjust the green chili and red chili powder to your personal heat preference. For a milder flavor, de-seed the green chili before chopping.