Prep Work -
Clean, wash and soak both the dals separately in two bowls of water for atleast 2 hours. Rinse and drain the water from the dals with a strainer before use.
the) Clean and cut the onions (two kinds as per requirement). Clean and sort the cilantro leaves (to be finely chopped before use), 2 green chillies (slit vertically at the centre), garlic cloves (to be crushed before use) and curry leaves as per requirement. Keep them all aside for later use.

Prep Work For Urundai -
Transfer the dals to a food processor jar. Add red chillies and fennel seeds into the jar. Grind them to a coarse paste.
Transfer the grinded mixture into a bowl.
Now into the bowl, add finely chopped onions, finely chopped coriander leaves, and salt to taste.
Mix well with the help of your fingers.
Shape them into small roundels. (I have made 14 small roundels).
Leave some mixture (for about 2 roundels to be added in the kuzhambu later while cooking).

Prep Work for Kuzhambu -
In a food processor jar, grind the grated coconut into a fine paste by adding few teaspoons water. Keep it aside in a bowl.
Also grind the tomatoes and 1 green chilli into a fine paste. Keep it aside in a bowl.

Steaming of Urundai -
Steam the urundai (dal roundels) on idli plates in the microwave oven for 3 minutes by changing the racks once in between. I have not greased the plates with oil.
Transfer them to a plate for later use.

(Alternatively you can steam the urundai on idli plates on gas for about 10-12 minutes. Also grease the idli plates with some oil by using your finger tips before placing the roundels so that they do not get stuck to the plate.)

Cooking of Kuzhambu -
Heat a pan/kadhai/wok, and add 2.5 tablespoons oil.
Once the oil is sufficiently hot, add the mustard seeds, fenugreek seeds, cumin seeds, fennel seeds, and temper them. Now add the crushed garlic and saute for about 30 seconds.
Then add diced onions, half of the curry leaves and a pinch of salt. (When you add salt while frying onions it fries them faster).
the) Fry till the onions become translucent.

Cooking of Kuzhambu -
Now add the grinded tomato-green chilli paste, turmeric powder, red chilli powder, and coriander powder. Mix well.
Fry till the masala is well cooked or oil starts leaving the sides.
Add the left over dal mixture to the pan and mix it well.
hai) Now add the dry mango piece with water into the pan.

Cooking of Kuzhambu - Add 3 more cups water, salt to taste, and mix well.
Boil for about 8-10 mins on low heat by covering with a lid.
ke) Remove the lid, add the grinded coconut paste and 1 cup water. (Add water as per required consistency).
Cover with the lid and simmer for about 2-3 mins on low heat. Remove the lid, and stir once. Check the salt by tasting the sauce, and if required add more salt. Mix well by stirring.

Cooking of Urundai Kuzhambu -
Now add the steamed urundai into the pan one by one. Turn them once so that they get soaked up on all sides. Then add the rest of the curry leaves and 2 whole green chilies. Cover with the lid and simmer on low heat for about 6-7 mins. The final consistency is medium thick.

Switch off and set aside to rest for atleast 3 hours before serving. This tastes better after resting time as the masalas in the sauce blend well with the urundai. Also the flavours pick up after resting time. (The consistency becomes thicker after resting time) Before serving heat it to lukewarm temperature.

Serve hot with steamed rice/idli/dosa with other accompaniments as per your preference during main. I personally prefer it with steamed rice and papadum.