Fish marinated with mustard and steamed inside banana leaf parcel — delicate and aromatic
Ingredients
- 500g fish fillets
- 1 tbsp mustard paste
- ½ tsp turmeric
- 1 green chilli sliced
- Salt
- Fresh banana leaves
- String to tie
Method
About Patot Dia Maas: Patot Dia Maas (literally "fish in leaf") is Assamese steamed fish — one of the most elegant techniques in Indian fish cookery, preserving all the delicate fish flavour while infusing it with banana leaf aroma. The technique is ancient: long before refrigeration or sealed cooking vessels existed, banana leaves were nature's own cooking parcels — flexible, aromatic, and capable of holding food intact through steaming or grilling.
Choose firm fish fillets: Use 500g of firm fish fillets — pomfret, mahseer, rohu, bekti, or any firm white fish. Avoid soft delicate fish like sole or plaice — they fall apart in steaming. The fillets should be about 1.5cm thick.
Clean and pat dry: Rinse the fish fillets under cold running water. Pat very dry with kitchen paper.
Make the mustard paste: Take 1 tbsp yellow mustard seeds. Soak in 2 tbsp warm water for 15 minutes — soaking removes bitterness. Grind to a smooth paste in a small grinder with 1 fresh green chilli and a pinch of salt.
Prepare the marinade: In a wide bowl combine the 1 tbsp mustard paste, 1/2 tsp turmeric powder, the 1 sliced green chilli, and 1 tsp salt. Mix well.
Marinate the fish: Add the fish fillets to the marinade. Use your fingers to gently coat each fillet with the paste — work the marinade into any crevices. Cover and rest for 15 minutes at room temperature. This is enough time to flavour the fish without breaking down the texture.
Source fresh banana leaves: Use 4-6 fresh banana leaves, large enough to wrap each fillet. Available at Indian groceries, particularly those with Bengali, South Indian, or Northeast Indian sections. The leaves should be deep green, glossy, and unbroken.
If banana leaves are unavailable: Substitute with parchment paper for a similar parcel cooking technique — the result is different (no leaf aroma) but still delicious. Aluminium foil works in a pinch but loses much of the dish's character.
The critical leaf preparation: Banana leaves are stiff straight from the package. Pass each leaf briefly over a low gas flame for 5-10 seconds — you will see the leaf turn slightly glossy and become noticeably more pliable. The heating breaks down the rigid plant fibres.
Check the leaf flexibility: Try folding a corner — the leaf should bend easily without cracking. If it still cracks, pass over the flame for 5 more seconds.
If you have no flame: You can soak the leaves in hot water for 1 minute, then pat dry. The result is similar but slightly less aromatic.
Cut leaves to size: If your leaves are large, cut them into rectangles roughly 25x20cm — large enough to fully enclose a fish fillet with overlap on all sides.
The parcel assembly: Place a flexible banana leaf flat on a work surface, shiny-side down (matte side up — the side that touches the fish should be matte). Place a marinated fish fillet in the centre.
Spoon any extra marinade on top: Drizzle any remaining mustard marinade over the fillet — every bit of flavour goes into the parcel.
Fold into a tight parcel: Fold the bottom edge of the leaf up over the fish. Then fold the top edge down over that. Then fold the left side toward the centre. Then fold the right side over. The fish should now be fully enclosed in a rectangular packet, like a small pillow.
Tie with string: Use kitchen string (or strips of banana leaf, traditional but trickier) to tie the parcel closed. Wrap string around the parcel twice and tie tightly. The string should hold the parcel together but not be so tight that it crushes the fish.
Repeat for all fish: Continue assembling parcels until all fish is wrapped — typically 4-6 parcels for 500g fish.
Prepare the steamer: Use a bamboo steamer or any standard steamer setup with a lid. Fill the bottom pan with water and bring to a rolling boil over high heat.
The critical steam temperature: The water must be at a vigorous rolling boil before the parcels go in — stable rapid steam is what cooks the fish through. Weak steam produces undercooked fish.
Place parcels in steamer: Once the water is at full rolling boil, arrange the parcels in the steamer in a single layer (do not stack). Cover with the lid.
Steam for 20 minutes: The 20-minute cooking time is the right balance for 1.5cm-thick fillets. Thicker pieces need 25 minutes; thinner pieces need 15.
Do not lift the lid: Avoid the temptation to check during cooking. Lifting the lid releases the trapped steam and slows the cooking, leading to uneven results.
Check the parcels: After 20 minutes, switch off the heat. Carefully lift one parcel out (use tongs — they are very hot). Cut it open with a knife. The fish should be opaque white throughout, easily flaking with a fork. The leaf should have darkened slightly and the kitchen should be filled with the distinctive banana-leaf aroma.
If undercooked: If the fish is still translucent in the centre, return all parcels to the steamer for 3-5 more minutes.
The presentation moment: This is what makes patot dia maas special. Place each unopened parcel on a serving plate. The traditional Assamese way is to bring the parcels to the table closed — each diner opens their own parcel at the table.
The ceremony of opening: Each diner cuts the string and unfolds the leaf. The aromatic steam rises dramatically — banana leaf, mustard, fish, and turmeric combining into one of the great Indian cooking aromas. This presentation is part of the dining experience.
Serve directly from the leaf: Eat the fish straight from the open parcel — the leaf serves as a natural plate. The mustard-infused fish juices have collected at the bottom of the parcel and are scooped up with rice or bread.
Serve with steamed rice: Serve alongside plain steamed rice — the most traditional Assamese pairing. Spoon the fish and its juices onto the rice and eat together.
For a complete meal: Pair with a simple dal and a green vegetable. The delicate fish is the star — supporting dishes should be mild and not compete with the banana-leaf aroma.
A cultural note: Patot dia maas appears in Assamese poetry and ceremonial cooking from the 17th century — it is one of the most refined dishes in the entire Assamese repertoire. The combination of natural packaging (banana leaf) and steam cooking represents centuries of culinary wisdom about preserving and concentrating flavour. Eating this dish connects you to a sophisticated cooking tradition that long predates modern packaging or appliances.
Leftover storage: Stored in the fridge with parcels still wrapped, this dish keeps for 1 day. Reheat by re-steaming for 5 minutes — never microwave, which destroys the delicate texture. The banana leaf flavour fades overnight; best eaten the day made.