First, rinse the moong dal under cold water until the water runs clear.
Drain well.
In a heavy-bottomed pot, combine the rinsed dal, water, turmeric, ground coriander, ginger, and green chili.
Bring to a rolling boil over high heat, stirring occasionally.
Reduce the heat to low, cover the pot with a tight-fitting lid, and let it simmer gently for about 1 hour, or until the dal is completely soft and broken down. For a pressure cooker, combine the with the reduced amount of water, secure the lid, and cook under pressure for 25 minutes. Allow the pressure to release naturally.
Once cooked, remove the pot from the heat.
Add the salt and use a wire whisk or an immersion blender to beat the dal until it is creamy and smooth.
Now, prepare the chaunk (tempering).
Heat the ghee or oil in a small pan over medium-high heat.
When the ghee is hot, add the cumin seeds.
Fry them until they sizzle and turn a rich brown, which should take about 30-45 seconds.
Carefully pour the hot, sizzling chaunk directly into the dal soup. Immediately cover the pot and let the aromatic flavors infuse for 1-2 minutes.
Uncover, stir in the freshly chopped coriander, and serve immediately.