Boil 1 Cup of water. Add the dried tamarind or kokum. Let it steep for 10-15 minutes till you do rest of the prep. If using tamarind paste, mix it in ½ cup of water.
Add 1 teaspoon salt, turmeric, ginger, and garlic to the shrimp. Mix and set aside.
Heat a pot on medium flame. Once hot, add the oil. Heat for 10-15 seconds.
Add the mustard seeds and cumin.When they start to splutter add the curry leaves and chili .Sauté for 10-15 seconds.
To this, add the chopped onion or shallots. Sauté till they are translucent. This should take 1-2 minutes.
Add the Kashmiri Chili powder and roast for 10-30 seconds.
Add the cleaned shrimp, kokum or ¼ Cup of tamarind or kokum water. Bring to boil.
The shrimp is cooked when it has turned orange and curled up.
Add the coconut milk. Let it heat through but don't bring it to boil
Check the salt and sourness. Add more of salt and tamarind/Kokum water if needed to balance the curry.
Garnish with Coriander or curry leaves. Serve hot.