In a pan heat 2 tablespoons of oil on medium heat.
Add the eggplants and cook on medium heat, turning often until the eggplants are little softened, around 10-12 minutes. You don't want them to be too soft, they will not be cooked all the way through, but that is ok.
Remove the eggplants from pan and place on a kitchen towel.
In the same pan add 1 tablespoon of oil on medium heat. Once the oil is hot add 1/2 tsp mustard seeds and let them crackle. Add 1/4 tsp each of onion seeds and fennel seeds.
Add chopped green chilli and curry leaves and mix.
Add chopped onions and cook, stirring often, until they are translucent, about 10 minutes. Add the ginger-garlic paste and cook till the raw smell goes away, around 2-3 minutes.
Once the ginger-garlic is cooked, add the dry spices - 1/4 tsp cumin powder, 1/2 tsp coriander powder, 1/2 tsp red chilli powder and salt to taste. Mix well to combine.
Cook the spices for 2-3 minutes, add around 1/2 cup of water to make sure spices don't burn.
Now add the remaining curry base paste to the pan.
Add 1/2 tsp turmeric powder and 1/2 tsp paprika powder and cook for 5-6 minutes on medium-low heat.
Add the previously fried eggplant into the curry.
Add 2 cups of water, cover and cook the curry on medium-low flame for 15-20 minutes until the eggplants are cooked all the way through.
Add 1/4 tsp garam masala, 1/2 tsp tamarind paste, sugar, if using, and mix. Allow to come to a boil and adjust flavour for salt and spice.
Turn off the heat and add some fresh coriander leaves and serve immediately.