Using a blender, make a smooth paste of the 2 tbsp of soaked dal that you reserved earlier, whole coriander seeds, cumin seeds, green chilis, cilantro, hing, and grated coconut. Set aside.
String the tamarind paste in 2 cups of water in a saucepan, and bring to a simmer.
Add salt, turmeric powder, jaggery, and the spice paste to the tamarind water. Continue to cook on a medium low fire until the Huli thickens a bit.
Adjust the desired tartness, spice, and sweetness in the Huli at this stage.
Add the steamed Undae to the huli and continue to cook for another minute before turning the heat off.