First, take 500 grams of chicken (cut into small pieces) in a pressure cooker and add 750 ml of water, ¼ tsp of turmeric powder, and salt as required to it. Then, cover the pressure cooker and cook it on a medium flame up to 2 to 3 whistles.
While the chicken cooks, take 2 tsp of peppercorns, 2 tsp of cumin seeds, 1 piece of ginger (inch-size), 10 cloves of garlic, and a handful of curry leaves in a mixer and grind them roughly. Transfer them to a bowl.
Now, take one medium-sized, roughly sliced onion in the same mixer and blend it to a coarse paste. Transfer them to a bowl. Also, blend 2 pieces of large tomatoes and keep aside.
Now, heat 2 tsp of ghee (clarified butter) in a pan on a medium flame. When it is hot, add ½ tsp of mustard (rai) and ½ tsp of cumin seeds to it. Let them crackle. Now, add, 2 pieces of dry red chilies and a handful of curry leaves. Sauté them for 10 seconds or so.
Now, add the onion paste and sauté for 2 minutes until it is dry. Then add the tomato paste and sauté for two minutes as well on a medium flame.
Now, add the coarsely powdered pepper and cumin along with 2 pieces of whole green chilies, ¼ tsp of turmeric powder, and ½ tsp red chili powder (optional) to it. Mix and fry them nicely for a minute or so. Now, add 3 tbsp of coriander leaves (finely chopped) to it and again sauté for about a minute on a medium flame.
Now, add the boiled chicken along with the water and the juice of a small gooseberry size tamarind, presoaked for about 15 minutes. Give it a nice mix and let it cook on a low flame until it starts to boil.
When the rasam starts to boil, switch off the gas stove. Garnish it with a handful of finely chopped fresh coriander leaves. Cover the lid immediately so that the flavor does not escape and leave it for 5 minutes.
Remove the cover after five minutes, give it a final mix and let it cook for another couple of minutes or so, this time without cover. Check the final consistency of the chicken rasam. Add water and cook for some time more if needed.
Your healthy and tasty homemade chicken rasam is ready to enjoy. Transfer it to serving bowl and serve it hot with steamed rice.