Served warm for lunch or bubbling hot for dinner, this dish is a great way to use up larger courgettes or marrows that appear at the end of the season, or if you find them lurking in your vegetable garden after going away for a week or so. You could use young skinny courgettes instead, but I find their flavour is so sweet I would rather shave them into long thin slices and dress them simply with barely a half clove of crushed garlic, some lemon juice, mint and olive oil.
The important thing to remember is to make sure, whatever the size, the slices are cooked until they are floppy and nicely charred. A cast iron grill pan is great, or a less heavy non-stick grill pan will work just as well. You just want the raised ridges to create those lovely charcoal lines that give the courgettes an added smokey flavour.
The consistency of the tomato sauce is quite key as it will affect how dry or watery the finished parmigiana will be. You can tell the sauce is ready when individual rising bubbles settle into one place and make a pleasant 'blip blip' sound. It should be thick enough to coat pasta, but still pourable.You could use only tinned tomatoes instead of the passata, but the sauce will need more reducing. In Tuscany there's a brand called Mutti who make an excellent tomato polpa (crushed finely).
I like to use a clear pyrex oven dish as it shows off the lovely red, green and pale yellow layers, but really any ovenproof dish will do, even a tall round one. The oval dish I used in the photo was 33.5cm by 22.5cm at its widest, and 6cm high.
Serves six as a main course, or many more as an accompaniment.
About 1.5kg of courgettes or marrows
425ml tinned tomatoes, crushed
750ml tomato passata
A small onion
Two level teaspoons of sugar
250g aged pecorino, or Corzano e Paterno's pasta cotta
A lemon, sliced in half
Salt and pepper
Preheat the oven to 180 degrees Celsius.
Heat a grill pan over a medium to low flame. Slice the courgettes into rounds roughly half a centimetre thick. Sprinkle with salt to draw out some of the moisture. The pan is ready when it starts to smoke, brush some oil lightly over the pan and quickly add a batch of courgettes, enough to cover the base with a layer. Char the slices for 3-4 minutes on each side and brush a little oil on any that start to look dry. Try not to overdo the oil as the courgettes should steam quite happily and excess oil will make the final dish greasy. Allow the courgettes to cool enough to handle.
While you wait, chop the onion into fine dice and sweat with salt and olive oil in a saucepan over a low heat. Try not to let them brown. When the onion is translucent and soft, add the tinned tomatoes and passata. Add the sugar but do not season until the sauce is ready to avoid overdoing it. Give everything a good stir, bring it to the boil then simmer gently until the sauce has reduced to a thickish, but still sloppy, consistency. Season with salt and pepper to your taste and allow to cool a little.
While the sauce reduces, coursely grate the parmesan and pecorino and mix together. There's no need to bother with super fine cheese.
Brush your dish with oil and start with a thin layer of tomato sauce. Cover with a layer of overlapping courgette slices until no sauce is visible, then squeeze over some lemon juice and season lightly. Next sprinkle over a thin layer of cheese; you will still see bits of green underneath. Repeat with a layer of tomato sauce first and continue layering courgettes, sauce and cheese until everything is used up. The last layer should be a thick topping of cheese to blanket everything else.
The parmigiana can be prepared in advance up to this point. If you freeze it do allow it to defrost thoroughly first.
Season the dish one last time, drizzle over with olive oil and pop it into the oven. It should take roughly an hour, check after 45 minutes. The cheese topping should be melted, golden brown and bubbling. The dish will be very hot, and can sit in the warmer or a turned off oven without coming to any harm.
Serve as a side dish, or with a lemony green salad and crusty bread as a main.