Steaming is a time-honored way of cooking fishes, mostly because the results are so good. Microwaves aren't exactly time-honored, but they seem to be a great way to steam fishes without ...well... steaming them.
The exotic Bengali word for steam is bhapa, and the most famous of the bhapa varieties are undoubtedly the one where mustard is involved. When wrapped in banana leaf, it's also called paturi. This is not the only way that bongs know to bring fish and mustard together, or even fish and steam - but it is the most well known.
Bhapa fish is a really simple dish; just two things are absolutely required - mustard paste and fish. And, of course, a wrapper of some kind to steam in - traditionally banana leaf, but I use parchment when that's not around. You coat the fish with the mustard paste and steam it for enough time; this yields a fairly interesting (if not wonderful) mustard fish. In India, it's made with hilsa - the holy grail of steamed fishes - or bhetki. Here, in the land of the hilsa-deprived, the fishes that works best are flaky, high-fat fishes such as halibut, cod, salmon or chilean sea bass. Shad, a common hilsa substitute, does not have enough fat. Salmon steak is easy to get and has a strong-enough taste to stand up to lots of mustard and tastes great though somewhat non-traditional (salmon isn't available in Bengal).
The best mustard paste is made using Colman's English Mustard Powder(only the powder, mind you, NOT the paste). However, this mustard, in the refined British way that the refined British are, is a smooth uniform yellow paste - very unexciting. You want your mustard a little flecked, a little stubbly, so to get a bit of texture I usually add freshly powdered black mustard (rai) seeds. They don't taste as strong as the Colman's, but look a whole lot more real. Make the paste dry, with just a tiny amount of water.
Now for the fancy touches. First, a thickener that makes the sauce cling to the fish. Once choice is posto (poppy-seed) paste. Don't go overboard - about a third the volume of mustard should be enough posto. Be light, posto doesn't have much flavour so too much of it will give you a very dull fish.
The other option (the one favoured by bong grandmothers) is fresh coconut ground to a fine paste. Add as much of it as you like; tastes great. No fresh coconut? Use a touch of canned coconut cream, though I recommend heating is slowly before to thicken it a little (and slow is important, or you will end up with coconut oil). I like coconut cream, so I add it anyway, even when there's fresh coconut. Also, you have to cool it before adding it to anything, or you'll end up cooking the fish with the sauce well before any steam can be let off.
Finally, the toppings - green chillies (deseeded) and kalonji (nigella seeds) crackled in oil. A few drops of raw mustard oil adds an extra kick. Mix up the paste, coat the fishes generously, then take a deep breath. Put a sheet of parchment (banana leaf, if you're intent on being fancy) on the table, place the coated fishes on the paper, wrap it in, fold and staple the sides closed (yes, staple - the kind you get at Staples). Then, put it into a microwave, remember to press the start button and wait. It's about usually three minutes per medium steak - about 250g (a little over 1/2 lb) of fish, but you'll have to experiment with your particular microwave and fish; luckily, it's quite tolerant and wont overcook easily.
A friend of mine wanted me to cook for her, but had no spices at home. We made a pact; I'd cook something truly Indian with only what's available at her local supermarket - which sounded like a huge challenge till I discovered her 'local' was a WholeFoods with neary every kind of spice there is.
Life, however, wasn't as simple as all that. First, each bottle of spice is at least $3; buying a decent complement would soon have made holes in pockets enough for spaceships to pass through. We decided therefore only to buy condiments that would be useful after the mess I made had been cleared up - that is, she could keep using them. Second, there were some critical missing ingredients such as besan, green chillies, ghee, mustard oil - all of which made cooking most standard Indian dishes (like the basic aloo-jeera or my superquick aloo golki) impossible. Chillies were a particular challenge - I've learned with experience that Mexican chillies don't work - the taste rather different. Third, we were looking at a kitchen devoid of kadahis or woks. The final blow? No basmati rice.
Here's what I was left with; ginger (not fresh), garlic, onions, tomatoes, potatoes, cilantro, chicken, black pepper, coconut milk, cumin powder, mustard powder (unfortunately not a very nice kind), yoghurt and garbanzo beans from a can. And some Hungarian paprika was already lurking in her cupboard.
(That was some boring paragraph above but how interesting can you make a grocery list sound).
Moving on. The ingredients resulted in a Chicken Kosha (with black pepper instead of chillies), chickpeas chaat and mustard aloo. I thought the first two were quite good, while the mustard potatoes was a complete failure (primarily because of a lack of green chillies and strange-smelling sweetish mustard). My American friends, however, loved the chaat and (rather to my surprise) the potatoes. The opinion on chicken; I thought it was quite nice (smelled great though not hot enough) but they were less than impressed. It seems they expected more flavors. So I'm wondering, is the chicken a failure because it looks like 'curry' but is just a simple homestyle dish or did I just cook badly?
I'm also thinking; what else that's India can be made with the output of a standard grocery? it need not be Whole Foods - even Albertsons or any other chain has all the ingredients I listed. And which one of those will impress women?