A revised, updated edition of my cookbook, Don't Sweat the Aubergine, comes from Black Swan on 26th April. Here it is, on the publisher's website. And here is what I have to say in the book about aubergines.
Nowhere in the literature of cookery is the sway of received ideas more evident than in the treatment of aubergines. Routinely, recipes advise you that aubergines should be salted, rinsed and dried before cooking. You leave them, sprinkled with salt, in a colander, perhaps with a plate on top to squeeze them a little, for half an hour or so; or, more rarely, you use the technique given in Classic Turkish Cookery by Ghillie Basan, who suggests you soak aubergine cubes or slices in salted water. Recipes may add the gloss that the point of the exercise is "to remove the bitter juices".
Once upon a time, it seems, aubergines were bitter. Some varieties still are, no doubt. But I’ve never found one. In any event, salting probably does not remove bitterness: it disguises it (cf McGee on Food and Cooking).
Supporters of salting who acknowledge the lack of bitterness in modern strains of aubergine advance a second reason for the practice: that pre-salted aubergines do not soak up so much oil when you fry them. It is true that unsalted aubergines soak up all the oil you give them as soon as they touch it. But salted ones soak up quite a lot too; and, if you have cut the vegetable into cubes and are stirring them around, the flesh soon starts sticking to the pan. Stuck bits apart, the cubes are usually still firm after the 10 minutes that recipes tend to give as the cooking time. Aubergine is not nice unless it is soft.
Delia Smith says that pre-salting concentrates the flavour, ensuring that the cooked aubergine won't be watery. I experimented. I pre-salted the cubes of half an aubergine; then I baked it with the cubes of the other half, salted only as I put them in the oven. I tasted each kind. There was no difference between them.
HOW TO COOK THEM
Cut aubergines into cubes. Put them on a baking tray or in a roasting pan, and pour olive oil or sunflower oil over them - about 1 tbsp for each medium-sized aubergine. Add salt, and pepper if you like. Toss with spoons, or with your hands. Cook at gas mark 6/200°C for 20 minutes to half an hour, or until tender.
Recipes such as Parmigiana di melanzane and moussaka require rounds (cut into 1/2cm discs horizontally) or slices (cut the aubergine in two horizontally, then cut 1/2cm vertical slices), according to your preference. Brush them with olive or sunflower oil (if you don't have a pastry brush, pour some oil into a small saucer, dip a fork into it, and brush the aubergine slices with the backs of the tines), season, and bake as above.
You can brush slices of aubergine with oil and cook them in a frying pan or a ridged grill pan, or on a barbecue. But I like the flesh of my aubergines to have a melting texture; and I find that texture harder to achieve by frying or grilling than by baking. Frying cubes of aubergine is, in my experience, very unsatisfactory: as I say above, the cubes soak up all the oil, stick to the pan, and take ages to tenderise. However, you can cook them in an pan on the hob if it also contains onions, which provide a moist environment. Cook the onions in oil first for about five minutes, tip in the aubergines with some salt, stir everything around, and cover. Cook on the lowest heat, stirring regularly. The aubergines should be tender in 15 to 20 minutes.
Another way of cooking aubergines is to bake them in their skins, then to mash up the flesh with garlic, oil, lemon, salt and any other flavourings you fancy. Tahini, the sesame paste with the consistency of peanut butter, works well. I like a dash of cayenne or chilli pepper. Cumin, dry roasted in a pan until it gives off a toasty aroma and then ground in a mill or mortar, is also nice. One clove of garlic, finely chopped or mashed, for each aubergine; 1tbsp of tahini; 1tbsp olive oil; 1tbsp of lemon juice; 1tsp of cumin seeds.
There’s a neat way of baking aubergines in Gordon Ramsay’s Kitchen Heaven. You slice the aubergine in half, slash the flesh, sprinkle one half with garlic, add oil, seasoning and, in his recipe, a sprig of rosemary, put the halves together and wrap them tightly in foil, bake at 220°C (gas mark 7) for 45 minutes, then at 110°C (gas mark 1/4) for a further 25 minutes (the aim is to get the flesh really soft). You scoop the flesh (discarding the rosemary, which will have imparted its flavour) into a pan. Then, Ramsay says, you heat it to evaporate the liquid and to achieve a thick, creamy consistency. So Ramsay clearly doesn’t think the juices will be bitter: this technique will concentrate them.
My one variation on Ramsay’s method is to add the oil at the end of cooking, in order to get its full flavour.
My favourite aubergine dish is Parmigiana di melanzane. You slice and bake the aubergines as in HOW TO COOK THEM above, layer them in a dish with tomato sauce (it doesn't matter whether you end up with tomato or aubergines or a mixture on top), put chopped mozzarella on top and grated Parmesan on top of that, then bake at, say, gas mark 4/180°C to blend the flavours and brown the cheese. It's delicious hot, even more delicious at room temperature, and most delicious lukewarm.