Preheat the oven to 220°C (425°F/Gas 7). Put the eggplant in a single layer on a tray and sprinkle with a little salt. Set aside for 10 minutes, then rinse well. Put the eggplant on a baking tray lined with baking paper, drizzle with half of the olive oil and cook for about 15–20 minutes, or until tender. Remove from the oven and set aside.
Heat the remaining oil in a frying pan over medium heat. Add the garlic and cook for 2 minutes, or until golden. Add the onion, capsicum and tomato. Pour in the water and season with salt and pepper. Bring to the boil, then reduce the heat and simmer for 45 minutes to 1 hour, stirring every 10 minutes or so — this mixture forms the binding agent for the pie so it needs to be quite thick. When it coats the back of a spoon use a stick blender to process until smooth. (If you don’t have a stick blender, transfer the mixture to a food processor and process until smooth then pour back into the warm pan.)
Add the beans to the pan and cook for 2–3 minutes, then add the zucchini and cook for 10–15 minutes, or until the vegetables are tender. Remove from the heat and add to a bowl with the eggplant, artichoke hearts, parmesan, salt and pepper, stirring well to combine. Allow to cool, then stir through the parsley and basil before filling the pastry cases.
Preheat the oven to 200°C (400°F/Gas 6). Roll out the savoury pastry following the instructions and use it to line the base and sides of six 12.5 cm (4¾ inch) pie tins. Roll out the puff pastry following the instructions and cut out six circles with a 13.5 cm (5¼ inch) diameter to make the pie lids.
Spoon the mixture into the pastry-lined pie tins, filling them to the brim. To attach the puff pastry lids, brush the rim of the pastry base and lid with a little egg wash and lay the lid over the base. Pinch gently between your thumb and index finger to make a good seal around the circumference edge. Brush the top of the pie lid with egg wash, sprinkle with nigella seeds, and make a small hole in the middle to allow steam to escape. Reduce the oven temperature to 180°C (350°F/Gas 4) and bake the pies for 30–35 minutes, or until golden brown on top. Remove the pies from the tins and leave to cool for a few minutes before serving.