Palermo-Style Aubergine Parmigiana

Start with the aubergine itself, because for five of them you're choosing at the shop, not just at the chopping board. Look for ones that feel heavy for their size and have taut, shiny skin — a light, dull aubergine has gone spongy inside, lost moisture, and will behave unpredictably in hot oil. Firmness under light finger pressure is your test, not colour. If you can't get good ones, courgette sliced the same way will take a parmigiana-shaped sauce reasonably, though it won't have that same soft, almost meaty collapse aubergine gives you — it's a stand-in, not a swap people should pretend is identical.

The onion in the sauce is doing a quiet job: it's sweetness and body, not flavour you're meant to notice as "onion." Chop it fine and fry it in olive oil until it turns from white to pale gold — past that, into brown, and it turns bitter, which then simmers for half an hour concentrating that bitterness into the whole sauce. If you've got a stick blender, you can blitz the sauce smooth after simmering and never notice whether the onion was diced neatly — most home versions do exactly this, because recovery from a mistake is easier than precision.

Tomato passata is already strained and smooth, which is the whole reason to buy it rather than tinned whole tomatoes for this — you want a sauce with no seeds or skin fighting the Parmesan and basil for texture. A litre for five aubergines and four people sounds like a lot until you remember it's reducing for thirty-plus minutes and then being spread in thin layers across a wide dish — you're not making soup, you're making a sauce that clings and doesn't run when sliced. Chilli powder here isn't about heat for its own sake — a pinch sharpens the sweetness of the tomato the way salt does, so taste before you decide you need more.

Two oils, two jobs. The vegetable oil for frying needs to be neutral and able to take real heat without smoking or arguing with the aubergine's own taste — any flavourless oil with a high smoke point does this: sunflower, groundnut, rapeseed if that's what's in the cupboard. The olive oil is for the sauce, where its own flavour is actually welcome, mixing into the tomato rather than being fried off and wasted — don't swap them. Frying aubergine in good olive oil is just an expensive way to burn olive oil's flavour away; save it for the sauce, where it survives.

On a British hob you won't have a wide, shallow kazan-style pan built for this kind of frying — use the widest frying pan you own, and fry in batches rather than crowding the pan. Crowd it and the oil temperature drops the second the slices go in; instead of frying, the aubergine stews in lukewarm oil, soaking it up without ever crisping even slightly at the edges — that's the actual mechanism behind "oily parmigiana," not a vague curse about aubergine being thirsty. Kitchen paper on a plate is your drain, and a second sheet over the top does the job of a lid if your dish doesn't have one — keeps splatter down while the next batch fries.

Three layers minimum, but it's the resting after that actually makes the dish. Hot, straight out of assembly, the layers are still distinct — sauce here, aubergine there, cheese not yet one with anything. Given a few hours, even just sitting at room temperature covered, the layers merge by capillary action — sauce soaks sideways into aubergine, cheese softens into both — and what you get sliced the next day holds its shape and tastes like one dish, not three stacked ones. This is patience as an ingredient, not an afterthought: don't serve it straight away expecting the full thing, because it genuinely isn't there yet. Feeds four generously as a side, or two if treated as a main with bread, in which case stretch to six people by widening the dish rather than the layers.