Marinate shrimp with salt, turmeric, chili powder, black pepper, and ginger garlic paste for at least 30 minutes.
Fry shrimp separately and set aside.
Fry mustard seeds and curry leaves in the same oil, until the mustard seeds start to pop.
Add onions and garlic, and sauté for a few minutes.
Add tomatoes and cook until soft.
Add coriander powder and cook for a few minutes.
Blend mixture using a hand blender, and add coconut milk.
Add fried shrimp, and cook on a low flame for 10-15 minutes.