Soak the kadalai Paruppu/bengal gram in water for atleast 3 hrs. I soaked it overnight. Cook it in a pressure cooker with just enough water for a whistle or two. Let it rest.
Finely chop the onions and garlic.
Cut off the root parts of the greens and clean it for any infected leaves. Wash the Thandu Keerai/Foxtail Amaranth twice in running water and let it soak in salted water for about ten mins. Finely chop the greens along with the stems.
In a pan, heat oil. Add mustard, jeera and split red chillies. As the mustards splutter, add finely chopped garlic pods. Fry until the raw smell is gone.
Add finely chopped onion and fry until translucent.
Add finely chopped greens. Add required salt. Stir well. Reduce the flame to medium. The greens would leave enough water to cook. Add the cooked Kadai Paruppu/Bengal gram and stir well.
As the greens have wilted, check if there is enough water content. If not, sprinkle some water (from cooking the Bengal gram) on top. Keep the pan closed and cook for 5-7 mins.
The greens should look cooked and without any water/moisture content. Add grated coconut and mix well.
Serve hot with rice and ghee or with sambar or rasam.
Notes
While cleaning the Amaranth leaves, look for any infected leaves or white/darks spots on the leaves. Remove such leaves.
The stem of this green is easy to cook and quite juicy, remove only the root part of it before starting to clean.
Soaking the green leafy vegetable in salted water (esp rock salt) can help reduce the microorganisms that infest on these vegetables.
If the Bengal gram is soaked for longer time, the cooking time would be quite less. Pressure cook it for only one whistle.
Coconut is optional but adds a good flavour to this stir fry.