Pressure cook the chana dal and yam with half of the turmeric powder, salt and water enough to cover them for 3 whistles.
In a pan, roast ¼ cup coconut until they turn light brown in color. Transfer to a plate. Then roast the red chillies until they are crisp.
Grind the ½ cup coconut, cumin seeds along with 2 tbsp of the roasted coconut and red chillies to a smooth paste adding water as required.
In a kadai, add ashgourd, remaining turmeric powder, jaggery, salt and enough water to cover them and cook until the ashgourd becomes soft.
Then add the cooked chana dal and yam. Mix well. Add the ground coconut paste, curry leaves, adjust salt if required and cook for 3-4 minutes.
In a small pan, heat coconut oil and add mustard seeds. When it splutters, add urad dal, red chillies and curry leaves.
Pour this over the koottu and add the remaining roasted coconut. Mix well.