Soak mustard seeds, green chillies, and poppy seeds (if using) in warm water for 15-20 minutes. Blend into a smooth paste with minimal water. Set aside.
Optional: Lightly fry paneer cubes in a bit of oil until golden brown, or use raw paneer for a softer texture.
Heat mustard oil in a pan until it smokes lightly (to mellow its pungency), then reduce heat. Add kalonji seeds and let them sizzle. Stir in the mustard paste and sauté for 2-3 minutes on low heat until the raw smell disappears. Add turmeric powder, salt, and slit green chillies. Mix well. Pour in water to make a gravy of desired consistency. Let it simmer.
Add the paneer cubes and cook for 5-7 minutes until they absorb the mustard flavours.
Optionally drizzle a few drops of raw mustard oil on top for an extra kick.
Serve hot with steamed rice.
Notes
Shorshe paneer is special for its pungent mustard-y gravy and is a bold- flavored vegetarian dish that tantalizes the palate. Shorshe paneer is cooked in mustard oil which adds an extra layer of sharpness and aroma.