Fish in Bangladeshi Shorshe Bata (Mustard Paste)

Preparation

1. Step 1

   Pour the juice of 1 lemon onto the fish fillets and sprinkle with ½ teaspoon of the salt and ¼ teaspoon of the turmeric; set aside.

2. Step 2

   In a spice grinder, combine the mustard seeds, remaining ¼ teaspoon salt, remaining ¼ teaspoon turmeric, 1 chile (or to taste) and the garlic. Grind to a smooth paste. Transfer to a food processor and add 3 tablespoons of the mustard oil, 2 tablespoons lemon juice, ⅓ cup of the cilantro and 3 tablespoons water. Process until smooth, adding more water if needed to get a paste with the consistency of cake batter.

3. Step 3

   In a large skillet over medium heat, heat 2 tablespoons mustard oil and add the spice paste. Let it sizzle for a few moments, and then use a wooden spatula to flip and stir it in the oil, reducing the heat if it starts to brown too quickly. Sauté until it darkens and thickens, about 10 minutes. Scoop the paste out of the pan and into a small bowl.

4. Step 4

   Wipe out the frying pan with a paper towel and return the pan to medium-high heat. Heat remaining 1½ tablespoons mustard oil. When the oil is shimmering, add the nigella seeds and, if desired, a whole green chile. Fry for a minute or two, then add the fish filets, carefully flipping them to brown both sides. When the fish is browned, add the spice paste and ¼ cup hot water or as needed to loosen the paste. Bring it to a boil and simmer until the fish is cooked through, about 5 minutes depending on the thickness of the fillets. Sprinkle with chopped cilantro.