Pat the fish fillet halves dry, place on a plate and season with 1 teaspoon of Pragati Turmeric and 1 teaspoon kosher salt. Cover and refrigerate for 30 minutes, or up to 2–3 hours.

In a small bowl, combine the remaining teaspoon of turmeric, dried mustard powder and powdered Guntur Sannam Chillies with a tablespoon of water to form a paste. Mix well and set aside.

Heat a large skillet over medium high heat. Add 2 tablespoons mustard seed oil and continue to heat for another 30 seconds. Place the fish in the pan in a single layer and fry until the fillets are just cooked through, about 1–3 minutes per side, depending on the thickness of the fillets. Transfer to a plate and set aside.

Return the skillet to medium heat and add the remaining tablespoon of mustard seed oil. Add the kalonji seeds and sauté until the seeds start to sizzle and pop, about 30 seconds. Add the shallot and chopped green chilli and continue to cook until the vegetables are softened and just start to caramelize, about 4–5 minutes.

Add the reserved mustard and turmeric paste and cook until the mixture starts to thicken and bubble, about 30 seconds to a minute. Add the coconut milk and stir to combine.

Add the reserved parcooked fish fillets back into the pan along with any juices that have accumulated and gently spoon some of the sauce over each piece of fish. Add the whole green chillies, cover and cook for 5 minutes. Remove the lid and cook until the sauce reaches your desired consistency, about 1–2 minutes more. (You’re looking for a thick, luscious consistency that coats and clings to the back of a spoon.) Remove from the heat and set aside.

To prepare the tadka, heat the mustard seed oil in a small saucepan over medium heat. Add the green chillies, mustard seeds and kalonji seeds and cook until the seeds start to sizzle and pop, about 30 seconds to a minute. Remove from the heat and stir in the powdered Guntur Sannam chillies.

To serve, transfer the fish to a shallow serving bowl and drizzle the tadka over the dish. Enjoy with plenty of basmati rice.