Trim the lower bottom of the bok choy bunch, separate each stalk and wash thoroughly. Chop them finely and wash again, drain and keep aside. Soak split green gram for 1/2 hour, wash, drain and keep aside. Now heat oil in a pan, splutter mustard, cumin seeds, dry red chili and curry leaves. Sprinkle asafoetida, add chopped onion, green chilies, garlic and fry for few minutes. Now add the green gram with 1 cup water, cover and cook over medium flame for 6 minutes or until its cooked fully. Add the chopped greens along with salt and cook further until the leaves gets wilted (about 3 minutes for baby bok choy and 5 minutes for matured stalks). When done add the grated coconut and chopped tomatoes, simmer for few seconds and switch off. Serve hot with rice topped with ghee.