Prep the Lentils: Sort through the lentils to remove any debris.
Rinse both dals well. If using toovar dal, soak it in 2 cups / 480 ml of hot water for 3 hours. If using yellow split peas, soak for 5 hours.
Drain the soaked lentils thoroughly before cooking.
Cook the Dal: In a heavy-bottomed pot, combine the 5¾ cups / 1. 5 liters of water, turmeric, ginger, green chili, and 1 tablespoon (15 ml / 0.5 fl oz) of ghee or oil.
Bring to a rolling boil over high heat. Carefully stir in the drained dals.
Once it returns to a boil, reduce the heat to low, cover with a tight-fitting lid, and let it simmer for 1½ hours, or until the lentils are completely soft and breaking down.
Finish the Dal: Remove the pot from the heat.
Whisk the dal vigorously until it becomes a creamy, smooth soup. For an even smoother texture, you can use an immersion blender.
Stir in the chopped coriander/parsley, lemon juice, and salt.
Prepare the Tadka: In a small pan, heat the remaining 2 tablespoons (30 ml / 1 fl oz) of ghee or oil over medium-high heat.
Once hot, add the black mustard seeds. They will begin to sputter and pop within seconds. As soon as they do, remove the pan from the heat and carefully add the curry leaves—they will sizzle instantly.
Combine and Serve: Immediately pour the hot tadka (the spiced oil) into the cooked dal and cover the pot at once.
Let the flavors infuse for 1-2 minutes.
Stir gently and serve hot.
