Recipe: Aubergine and courgette lasagne from The Italian Pantry by Theo Randall

Theo Randall gives his recipe, based on his mother's, for a vegetable lasagne

My mother used to make the most delicious lasagne – I used to get so excited when I knew it was coming. She was brilliant at making the béchamel sauce – it was always perfectly creamy but never thick and floury. The trick to this was to cook it very slowly and use equal quantities of flour and butter.

This is a vegetable lasagne, but it has as much flavour as the traditional meaty offering because you roast the aubergines (eggplant) first. Try to use egg-based lasagne sheets as they tend to have more flavour and are not as brittle when you cook them (or, better still, make your own sheets of pasta).

Serves 6

• 4tbs extra-virgin olive oil
• 2 red onions, finely sliced
• 500g courgettes, cut into 1cm rounds
• 1 garlic clove, finely sliced
• 500g tomato passata
• 8 basil leaves, roughly torn
• 3 aubergines sliced into 2cm rounds
• 300g egg-based dried lasagne
• Sea salt and freshly ground black pepper

For the béchamel

• 75g unsalted butter
• 75g plain flour
• 500ml whole milk, warmed to just below boiling point
• 150g Parmesan, grated, plus extra for sprinkling

Preheat the oven to 200°C/180°C fan. Heat 1 tablespoon of the olive oil in a non-stick frying pan over a medium heat. Once hot, add the onions, courgettes and a good seasoning of salt. Cook for 20 minutes, until the onion and courgettes are soft.

Heat another tablespoon of the olive oil in a separate saucepan, then add the garlic. Fry the garlic for 30 seconds, then add the passata and cook the mixture gently for 20 minutes, until reduced by half. Season with salt and pepper, then stir through the basil.

Brush both sides of the aubergine slices with olive oil and season them with salt. Place the aubergines in an even layer on a baking sheet lined with baking paper. Bake them for 15 minutes, then turn them over and bake them for a further 15 minutes. Remove the slices from the oven and, when they are cool enough to handle, cut them into halfmoons.

Set them aside and leave the oven on.

To make the béchamel, melt the butter in a medium saucepan over a low heat. When the butter has melted, add the flour and cook it out for a couple of minutes, stirring to combine. Next, add the hot milk and stir continuously to avoid any lumps forming. Cook the sauce gently for 20 minutes, stirring all the while, until smooth and thickened, then mix in the Parmesan and check the seasoning. Leave to one side.

Mix the aubergines, courgettes, onions and tomato sauce together in a large bowl and check that everything is seasoned well.

Use the remaining olive oil to oil a baking dish, then place a layer of lasagne sheets in the base of the dish. Add one-third of the vegetable mixture in an even layer, then top this with one-quarter of the béchamel sauce. Repeat this twice more, then finish with a layer of lasagne sheets and a final layer of béchamel sauce. Sprinkle the top with some more Parmesan, then bake the lasagne for 35 minutes, until the top is golden. Serve with a little extra grated Parmesan on top, if you like.