Picnic pie

For the shortcrust pastry:

1 Rub the flour and the butter together in a large bowl until the mix resembles fine breadcrumbs. Alternatively, pulse together in a food processor.

2 Add the salt, followed by the eggs, adding one by one.

3 When the dough starts to clump together, turn it out on to a lightly floured surface and bring together using your hands. Wrap the pastry in clingfilm and chill in the fridge for at least one hour.

For the filling:

1 For the aubergines and courgettes, slice the vegetables lengthways, about 5mm thick, and toss in a large bowl together with the chopped rosemary, two tablespoons of olive oil, salt and pepper. Fry or griddle the slices in a large frying pan or griddle pan for about five minutes, until softened slightly (do this in batches). Set aside on a tray or plate and leave to cool.

2 For the peppers, drain and slice into strips.

3 For the spinach and ricotta layer, put the spinach in a colander over a sink and pour over hot water from the kettle or tap to wilt. Cool slightly. Put the ricotta, lemon zest and cooled spinach into a large bowl, season with salt and pepper and mix well. Set aside.

4 For the caramelised onion layer, finely slice the onions and sauté on a low heat with a tablespoon of olive oil for about five to 10 minutes, until soft. Add the balsamic vinegar and sugar, season with salt and pepper and continue to cook for a further five minutes. Remove from the heat and cool.

To assemble:

1 Preheat the oven to 180 degrees or 160 degrees if using a fan oven. Line a 23cm round, loose-bottomed springform tin with parchment paper.

2 Roll out two-thirds of the pastry on a floured surface and line the base and sides of the tin, leaving a little overhang.

3 Sprinkle half of the Parmesan on the base of the pie, then begin to layer up the cooled vegetables, starting with the aubergines and courgettes, followed by the peppers, spinach and onions. Scatter the remaining Parmesan on top.

4 Brush the beaten egg around the edge of the pie. Roll out the remaining pastry, place on top and crimp the edges with your fingers to seal. Snip a hole in the pastry top and brush with the beaten egg.

5 Bake the pie in the oven for 45 minutes, or until golden. Leave the pie to cool for at least 10 minutes, before taking out of the tin to cool completely.