Soak the toor dal for at least 2 hours. This step is optional but I find that it really helps to get smooth and mushy cooked toor dal on pressure cooking
Place the soaked dal in a vessel with enough water to cover it by an inch or so
Add turmeric powder to the dal and place the vessel inside your pressure cooker with water in the base. I find that this helps the dal not overflow as it pressure cooks
Let the dal cook for 20 mins or 4-5 whistles and turn heat off. Let the steam escape
In the meantime, soak the tamarind in 1 cup warm water
Extract the juice and discard pulp and seeds
Wash and remove the stems from the baby brinjal (kathirikai)
Make large slits in them and place in a large cooking pot along with the tamarind and 2 more cups of water
Bring to boil and simmer until the brinjal is cooked soft
By this time, the pressure cooker should be ready to be opened
Mash the dal with the back of a spoon and add to the tamarind brinjal mixture
Bring to boil adding more water if the sambar seems too thick
Add salt and turn off heat
Heat oil for tempering in a pan
Add the mustard seeds and when they pop, add the chopped shallots and curry leaves
Fry until the shallots turn golden brown
Add hing
Then add 2 heaping teaspoons of sambar powder to the hot oil and turn off heat
Fry the sambar powder in the resulting heat
Add the tempering to the cooked dal brinjal mixture and mix well
Adjust salt as needed
Serve kathirikai sambar hot with rice and any curry