In a small pressure cooker, heat 1/2 tsp coconut oil. Roast the mung dal until aromatic and lightly golden. Add water, turmeric, salt. Pressure cook for 2 whistles. If you donu2019t have a pressure cooker, boil this in an open pan on the stove top for 15 minutes or so until the dal is cooked to a mush.
In a mixer jar, grind the chili, coconut and cumin to a smooth paste using 3-4 tbsp of water.
Add this paste to the cooked dal and bring to a simmer. Remove this into a serving bowl.
Heat the oil in a small pan. Add mustard seeds. Once it splutters, add the curry leaves and red chillies. Transfer this tempering over the parippu curry.
Serve along with red rice, Kerala sambar, avial and other side dishes as a part of Onam Sadya.