In the bowl of a food processor, place flour, butter and salt. Pulse a few seconds at a time until the mixture has a grainy texture. Add the egg, oil and water. Pulse again a few seconds at a time until the dough begins to form a ball. Add a little water if necessary. Remove the dough from the processor. Form a ball with your hands. Cover with plastic wrap. Refrigerate for 30 minutes.
Mashed Sweet Potatoes
In a saucepan, sauté the onion and sweet potatoes in the butter for 2 minutes. Add the water and bring to a boil. Season with salt and pepper. Cover and simmer gently for about 25 minutes or until the potatoes are tender.
Meanwhile, roll out the dough on a floured work surface. Line a 25-cm (10-inch) quiche plate. Refrigerate for 30 minutes.
With the rack in the lowest position, preheat the oven to 180 °C (350 °F).
In a food processor, purée 750 ml (3 cups) of sweet potatoes, the flour and cloves until smooth. Blend in the eggs. Season with salt and pepper.
In a bowl, gently blend the mashed sweet potatoes with the remaining potatoes cubes. Adjust the seasoning. Spoon into the crust. Bake for 30 minutes.
Sprinkle the pie with the cheese. Lay the zucchini in a rosette pattern, starting from the outside and moving inward. Scatter the olives evenly over the pie. Drizzle with the oil. Season with salt and pepper. Bake for about 30 minutes. Allow to cool slightly and serve.