To begin, take the cleaned prawns and marinate them in a bowl with 1/2 teaspoon of turmeric, 1/4 teaspoon of salt, and the juice of half a lemon. Mix well, ensuring the prawns are evenly coated. Set aside for 15-20 minutes. This will enhance the flavour and tenderize the prawns.

In a large skillet, heat 2 tablespoons of vegetable oil over medium heat. Once the oil is hot, add the mustard seeds and fenugreek seeds. When they begin to splutter, add the finely chopped onions and sauté for 6-8 minutes until golden and translucent.

Add the minced garlic, ginger, and slit green chilies to the skillet. Sauté for 2-3 minutes until the raw aroma disappears, stirring continuously to avoid burning.

Next, add the pureed tomatoes to the skillet, along with ground coriander, ground cumin, red chili powder, and the remaining turmeric. Stir well to combine. Cook for 5-7 minutes, allowing the mixture to thicken and the spices to blend.

Add the marinated prawns to the skillet, gently stirring them into the tomato and spice mixture. Cook for 3-4 minutes until the prawns start turning pink and firm. Be careful not to overcook the prawns at this stage, as they will continue cooking in the next steps.

Pour in the coconut milk and 1/2 cup of water. Stir gently, ensuring the prawns are submerged in the curry sauce. Bring the mixture to a gentle simmer, then reduce the heat to low. Cover the skillet and let it cook for 5-7 minutes.

Remove the lid and check the consistency of the curry. If it’s too thick, add a little more water. Stir in the garam masala and adjust salt to taste. Allow the curry to simmer for another 2-3 minutes, ensuring all the flavors are well combined.

Turn off the heat and garnish the prawn curry with freshly chopped cilantro and a squeeze of lemon juice. Serve hot with steamed basmati rice or naan, allowing the delicate balance of spices and creamy coconut to shine. Enjoy this rich and aromatic Indian prawn curry, perfect for a cosy meal.