My grandmother is known to make the best vathakozhambu in the family and here is the recipe!
Tamarind extract (1 lemon sized ball)
Mustard seeds, 1 sp, oil 3 tbsp
methi seeds 1/8 sp
1/2 sp channa dal
1/2 sp groundnuts
1 cup small onions/pearl onions/ kutty vengayam/ shallots
2 sp sambhar podi/ kozhambu podi
1 dried red chilli, curry leaves-1 sprig
salt, hing 4 dashes, turmeric 1/4 tsp
Add oil in a kadai. Splutter mustard seeds, add methi seeds, curry leaves, channa dal, ground nuts. Fry till golden brown. Add onions. Sprinkle salt. Let it cook till the onions are soft. Add 2 tsp of kozhambu/sambhar podi. Fry till the sambar podi is well roasted. Add more oil if required. After 2 minutes, add the extract of tamarind. Add salt, turmeric, hing. Let it boil well till the oil separates out. Check for salt. You can now add more water to achieve the correct consistency. Add 1/8 tsp jaggery to balance the sharp sour taste of tamarind.
Small onions is the most common veggie used in venthaya kozhambu. Any veggie like drumsticks, ladiesfinger/okra, red pumpkin etc can be used.
When sundaka vathal or manthakalika vathal is added, it is called vatha kozhambu. However when you use a dried vathal, make sure that you fry it well and add it at the end like a garnish. If you add it in the beginning itself, the vatha kozhambu might get bitter.
Manthakalika Vathal Kozhambu
Photo Courtesy: Padmini, Srinivasan (my parents)
Also be careful with the amount of salt you add to the kozhambu. Vathal has a lot of salt. Use less salt when you make vathal kozhambu.Note: For thickness in the kozhambu, 1 tsp of kadalai maavu (besan) can be added along with the sambhar podi and fried well with the kozhambu/sambar podi..