
Put the flour, semola, baking powder and salt in a large mixing bowl and mix them together. Add the olive oil and water and mix to form a rough dough.
Place the dough on a clean work surface and knead for a few seconds into a ball. Cover the dough with the mixing bowl (or use plastic wrap) and leave it to rest for 1 hour.
For the tomato topping, put the passata in a bowl with the oregano, crushed garlic clove, a pinch of salt and pepper and a drizzle of olive oil. Mix until combined, then set aside.
For the potato topping, thinly slice the potatoes as thin as possible (I keep the skin on but you can peel it if you prefer) then set them aside.
Pre-heat the oven to 250C (480F). Grease a baking tray generously with olive oil.
When the dough has rested, cut it into 4 quarters. Lightly dust your work surface with semola and roll one quarter of the dough out into a long thin pizza using a rolling pin. Make sure you roll it out long enough to fit your tray (our tray is 17x11.5 inches).
Lay the dough on the baking tray and cover it with tomato sauce all the way to the edges. Repeat with the rest of the dough (I usually do this in 2 batches as I can only fit 2 on a tray at a time).
Bake in the oven for 10 minutes, then remove them from the oven and spread on another layer of tomato sauce. Bake for a further 10 minutes, then remove from the oven and serve.
For the potato topping, drizzle your rolled out dough with olive oil then lay thin slices of potato over the dough, sprinkle with sea salt, fresh rosemary and then a drizzle of more olive oil.
Bake in the oven for 15-20 minutes until golden around the edges.