Preheat the oven to 190°C.
Heat the olive oil in a large, heavy-based saucepan over a medium heat. Sweat the onion and courgette for 4-5 minutes, stirring occasionally until they start to soften. Add the tomatoes and continue cooking for 4-5 minutes, stirring occasionally. Season to taste with the dried thyme, finely grated Parmesan, salt and pepper. Remove from the heat and set to one side.
Divide the pastry in half and roll one half out on a lightly floured surface to a 12inch square with a thickness of ½cm roughly. Use it to line an 8 inch square springform baking tin, pressing carefully into the corners. Trim any overhanging pastry and discard.
Roll the other half of pastry out to an 8 inch square on a lightly floured surface; this will be the lid. Fill the lined pastry with the vegetable mixture, then lay the pastry lid on top, sealing well at the seams, crimping the edges to create a rim. Brush the top with the beaten egg and make a small slit in the centre of the pastry.
Bake for 35-45 minutes until the pastry is golden and cooked through. Remove and allow to cool on a wire rack before turning out and sitting on a chopping board lined with parchment paper. Cut a corner away from the pie, then garnish the remainder with the shaved Parmesan and a few basil leaves on the top of the pie before serving.
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