Soak dal in water for 2 to 3 hours. Wash and drain water. Grind both the dals, red chilli, saunf to a coarse paste. No need to add water.
Add chopped onion, garlic, green chilli, ginger and grated coconut. Then add coriander, curry leaves and salt to the dal and mix well.
Make small balls of equal size. Grease an idli plate with little oil and place the balls carefully. Steam it for 10 to 15 minutes (you can also skip this step and add the balls directly to kuzhambu when it starts boiling). Keep it by side. Soak tamarind in water and extract tamarind puree.
For making Kuzhambu
Take a kadai, add 1 tsp of oil and roast all the ingredients given in the table 'To Roast and Grind', except coconut. Switch off flame, add grated coconut and give a quick stir (If you want to short cut the process, just add chilli powder and dhania powder to the kuzhambu, grind coconut alone). Cool down and grind everything with little water.
Chop onion, tomato and garlic finely. Take a heavy bottom vessel, pour oil and temper with the items listed in the table 'To Temper'. Now add onion and fry till transparent.
Then add garlic and tomatoes, saute well. Add tamarind extract, turmeric powder and salt.
When its start boiling, add the grinded paste. Keep boiling for 10 minutes in low flame. Now add the steamed urundai's one by one carefully. Also boil the kuzhambu for another 5 minutes, until the urundai's float on top and oil separates.Garnish with coriander leaves. Serve it hot with rice and appalam.
Tips for Urundai Kuzhambu Recipe
1. You can also use any one type of dal for making urundai's. 2. Add shallots which lends nice taste to the urundai kuzhambu recipe. 3. Also use gingelley oil which gives nice authentic taste to the recipe. 4. Thalippu vadagam adds nice aroma to the kuzhambu, but if you don't have in hand it can be omitted. 5. For simple version, add chilli powder, dhania powder or 1 tblsp of sambar powder to the kuzhambu. Skip the other ingredients in the 'roast and grind part', just grind coconut alone and add it. 6. Steaming the urundai method is always safe for beginners. 7. You can also add the urundai's directly to the kuzhambu. But be sure you add it once it starts roll boiling. 8. Add salt separately for urundai and kuzhambu. 9. Don't stir the kuzhambu after adding the urundai, until they float on top or else it will break. 10. This paruppu Urundai Kuzhambu thickens with time, adjust water accordingly. 11. Always prepare this paruppu urundai kuzhambu 2 hours prior to lunch, so that urundai's absorbs the kuzhambu and tastes good.