Peel the squash. While the peel is edible, my mother never used it for this recipe and neither do I (habit?!). I instead opt to use the peels to make a chutney out of it for the same meal.
Cut it in the center and remove the seed.
Boil it in enough salted water to cover it. You can also steam if you prefer it. It takes about 5 minutes to get tender. Drain and set aside. (I usually add the leftover water to my rasam
While that's cooking on the side, heat up a skillet with 1 tsp Coconut oil (or any other oil of your choice). Add mustard seeds. When they finish popping, add the urad dal, asafoetida and red chilli (if using. I haven't used it.)
When the black gram starts browning, add the coconut. Stir it for few seconds (just enough to toast it and remove the raw taste).
Add the chayote to the tempered ingredients along with turmeric and curry leaves.
Give it a gentle mix until combined. Taste and season with salt if necessary given that you boiled them in salted water.