To make the dough, stir the yeast into the water in a large bowl, add the olive oil, the flours, salt and oregano and stir with a spatula until it comes together. Turn it out onto a lightly floured surface and knead by hand for 3 minutes. You can do it in a standing mixer but you’ll miss out on the pleasure of handling the dough – and a mini upper arm workout. Let it rest for 15 minutes, then knead for another 3 minutes; by then it will be smooth and silky.
1. Divide the dough in two and shape each piece into a ball. Place them on a floured tray, well-spaced apart, cover with a damp tea towel and leave at room temperature for 3-4 hours or in the fridge overnight.
2. To make the onion topping, sweat the onion with the olive oil and a pinch of salt for about 30 minutes over low heat, stirring occasionally. At the end add the sugar and vinegar and cook them for couple of minutes more until they darken slightly. Set aside to cool.
3. To make the pizza, preheat the oven/grill to the maximum setting with a rack on second position from top. Place a large cast iron pan or flat griddle on the hob to heat up until smoking.
4. On a generously floured surface stretch one ball of dough at a time to a disc roughly the size of the pan (if you chilled the dough, take it out at least 40 minutes before shaping). Place it on a pizza peel or a small rimless baking sheet, with a disc of parchment underneath the dough if you’re worried about sliding it off the peel.
5. Arrange half the mozzarella slices on the dough, scatter basil leaves if using, spoon half the tomato sauce in blotches and sprinkle the sauce with chilli flakes. Spoon half the amount of onions over the sauce, scatter half the capers and olives and finish with parmesan, if using.
6. Transfer the pizza onto the pan or griddle using the peel or the baking sheet, fold the edges gently if the dough is larger than the pan, and immediately transfer to the preheated oven/under the grill.
7. Bake for 5-7 minutes until scorched, bubbly and looking good. Carefully slide it off the pan onto a wooden board and slice.