Rinse and soak paasi paruppu or yellow moong dal for 15 minutes. Pressure cook dal for 2-3 whistles until soft and mushy.
Rinse Pudalangai, cut both ends. Hold pudalangai firmly on a chopping board and run the knife lengthwise from top to bottom.
Using knife or spoon, scoop out the soft flesh and seeds from each side of the pudalangai. Finely chop and keep aside.
Pressure cook pudalangai and 1/2 cup chopped carrot with turmeric powder for 1 whistle. Let the pressure release naturally before opening. You can also steam the vegetables in a steamer pot.
Meanwhile, in a chutney jar, add 1/2 cup grated coconut, cumin seeds and whole dry red chilies. Grind to a smooth paste using about 1/2 cup water. Keep aside.
Mash the cooked lentils with a whisk. Heat a pan, add the cooked vegetables and lentils. Add salt to taste and let it cook for 1-2 mins.
Add some water, coconut gravy and mix well. Taste check and add salt, if required. At this stage, feel free to adjust consistency by adding more water.
When Kootu starts simmering, switch off heat and prepare for tempering. Do not boil Kootu.
Heat a small tempering pan, add oil, mustard seeds, urad dal, dry red chilies broken into 2-3 pieces and curry leaves. Curry leaves will splutter.
Pour tempering over the kootu. Cover and let it rest for 1-2 mins. Mix and serve.