Here's how I make it. Try it and chances are it'll creep into your 'favourites' list too, if it isn't already there :)
Get a couple of green cooking bananas. Pick fairly firm ones and avoid the ones that have a slight yellowish tinge to them (which means they're probably ripening). If you live in Aussie land, you can find them at most fresh fruit 'n' veggie stores or your local Indian store.
Then, wash and peel them. Try not to take off too much of the insides while you peel. Just lightly run your knife down the sides and get rid of the fibrous green skin.
Now slice each banana in half and then quarter. Next, slice into bite sized wedges, neither too thin nor thick. Make sure the pieces are somewhat similar sized to ensure even and fast cooking.
Then heat about a tablespoon of oil in a pan or wok (non-stick works really well). Once the oil is hot, add 1/2 a teaspoon of mustard seeds and let them crackle. Next add 1/4 teaspoon whole cumin, a pinch of hing (asafotieda) and a pinch of turmeric. Also add in some fresh curry leaves (yum!).
Tip in the sliced banana and give it a good mix so that they are coated well with the tempering.
Saute, uncovered until the bananas are well cooked. Somewhere in between the cooking process, add salt and chilli powder to taste and mix well. You should be aiming for them to turn out sort of crispy, sort of tender, well cooked and well flavoured. This really shouldn't take very long, say about 10 - 15mins.
You could cover the pan to speed up the cooking process, but I don't like to do that as the whole dish tends to get a bit soggy.
Do make sure it is well cooked. Under cooked green bananas are notorious for not-so-pleasant tummy issues :)
This is a great dish to serve on the side if you're cooking a south Indian feast.