Wash and chop snake gourd into small pieces. Soak chana dal in enough water for 30 minutes.
Heat oil in a pan, add mustard seeds, urad dal, curry leaves, green chilli, and dry red chilli. Sauté until fragrant.
Add soaked chana dal and stir for 2–3 minutes.
Add chopped snake gourd pieces, turmeric powder, sambar powder, and salt. Mix well.
Pour 1 cup of water, cover, and cook on medium heat until both snake gourd and dal turn soft (10–12 minutes). Add more water if needed.
Once cooked, sprinkle grated coconut and coriander leaves. Mix gently.
Serve hot snake gourd kootu with steamed rice, curd rice, or as a side with chapati.