1. Take a whole gutted, cleaned, de-boned bhetki (or shinghara or kingfish), split open like a book.
2. Marinate in paste of haldi, red mirchi, lemon juice for few hours, then wash. Make deep angled incisions on both sides.
3. Rub in a mixture of grated onions, ginger, salt and mustard oil, plus ground yellow and black mustard seeds, green chillies, salt and lemon juice.
4. Use a filling of your choice to stuff the fish with, such as small prawns with coconut in a ginger, red chilli and onion paste.
5. Cover fish in curry leaves and grated lemon rind, then wrap in a large banana leaf or foil.
6. Bake in a pre-heated oven for an hour. Before serving, pour some heated mustard oil over the fish so that it gets slightly singed.