A little sunflower oil, 1 onion chopped finely, 1 leek chopped finely (or peppers or celery), 2 large sweet potatoes cut into small dice, half a dozen small new potatoes cut into small dice, 3 green or unripe bananas (or platanos if you live in Spain) sliced into chunks, a wineglass of white wine, half a pint whole milk, quarter of a pint single cream, a pint of vegetable stock, 2 or 3 filets of any white fish - cod or hake is excellent - skin removed and chopped into rough chunks. To garnish: spring onions sliced finely or parsley chopped fine and a dash of lime juice.
Saute the onion in the olive oil until soft but not coloured. Add the leek (or the substitute peppers or celery) and continue to cook over a low heat until all is quite soft.
Add the diced potatoes - both sweet and new. Continue to cook on a low heat until the potatoes start to soften.
Add a wineglass full of any white wine you fancy and ramp up the heat a bit. Scrape the base of the pan to get any stuck on bits of veg loose.
Next you add the stock and the cream. Now if you were to use fish stock the end result would be much fishier in flavour than if you use veggie stock... its up to you... all I had in the cupboard was chicken stock and it didn't make that much of a difference.
Add the unripe bananas (if they are a little soft then you can add them at the same time as the fish) and then simmer on a low heat until the potatoes are all nice and soft. I put a lid on the pot to stop too much liquid evaporating but you can cook it without a lid... just keep an eye on it to make sure it doesn't reduce too much. You might get a froth from the cream rising to the top, you can ladle this out if you prefer but I just stir it back in and don't worry about it.
Once the veg is well and truly cooked and the sauce is nice and thick add the fish. I would usually skin the fish first but I was in a rush today and I totally forgot. Its not too much of an issue to remove the skin once its on your plate.
Simmer the fish in the stew for around about 15 minutes. You don't need any more than that or your fish will be tasteless.
Taste the stew and adjust seasoning. You will probably need salt - although I have popped a couple of anchovies into the stew at the simmering potatoes stage and that not only adds flavour but salt too. A good pinch of black pepper is also needed. If you wish to garnish, by all means add some fresh parsley or chopped spring onions and a squeeze of lime juice. Ladle into your bowls and tuck in!