Place a vessel over medium heat and drizzle two tablespoons of oil. When the oil heats up, add mustard seeds and split black gram.
As the mustard seeds start to sputter, add red chilies, curry leaves and continue to saute for 30 more seconds.
Now add chopped onions and saute it until onions turn transparent.
Add turmeric powder, red chili powder, saute for at least a minute.
Add salt, tamarind paste and continue to saute for 30 seconds.
Now, gently mash the boiled potatoes(I cooked my potatoes in Instant Pot pressure cooker) and add to the spice mixture.
Add a little water(¼ - ½ cup) to help mix the masala uniformly.
Mix well and cook for another 5 minutes. Garnish with cilantro/coriander leaves.