Add the nigella seeds, let them splutter a little then add the onions
Saute the onions until just translucent and then add the garlic and ginger paste, cook for a minute
Now add the chilli powder, turmeric, and ¾ tsp salt
Cook till the oil rises a little to the top then add curry sprig and 3 tbsp of the tomato paste, stir to mix
Pour in the coconut milk, a pinch of sugar, mix well and bring to a boil.
Add the shrimp, let cook just until the shrimp forms a open C shape.
Adjust consistency with water per your liking ( I usually add a small splash) then taste and add more tomato paste if needed and the green chillies (if using)
Serve with plain rice
Notes
This is a less is more recipe, keep the ginger-garlic levels scant for best flavour
If you wish to double it then put in 1 ½ tsp red chilli powder in the first round, 2 becomes too much somehow.
For a smooth curry blitz the cooked onions and spices together with a little coconut milk and then return to the pot and add curry leaves and remaining ingredients. Otherwise just mince the onions super finely and enjoy!