In a large bowl, dissolve the sourdough starter with still, room-temperature water, pouring it in slowly. Add the flour, a little at a time, and mix until the dough is smooth and homogenous. Cover it with a cotton cloth and leave it to rest in the fridge for 20 minutes. After which, pour 2 spoonfuls of olive oil into the bowl, add the salt and, again, mix well. Tip the dough out onto a work surface sprinkled with a little flour, stretch it out and fold it over on top of itself. Then put it back in the bowl and leave to rise for another 20 minutes. Repeat this procedure two more times and then, finally, put the dough back in the bowl greased with a spoonful of oil; cover with cling film and leave in the fridge for 12 hours. When the time is up, take the bowl out of the fridge and leave it at room temperature for about half an hour. Transfer the dough onto a floured work surface, spread it out and fold it over on top of itself, then knead it again until a ball forms (take care to avoid the air escaping from the dough). At this point, leave the ball of dough to rise until it doubles in size (it may take between 2 and 3 hours, depending on the temperature of the room). When it has risen, use your hands to spread the dough out in the baking tins – which you have greased with a spoonful of olive oil – and leave to rest for an hour. Now you can put the topping on the focaccia: distribute the tomatoes over the surface – “pushing” them well into the dough – and sprinkle with salt and oregano. Leave to rest again for 45 minutes and then bake in a preheated, ventilated oven, at 230 °C, for 10 minutes on the lowest shelf and another 20 on the middle one. Remove them from the oven and, while still hot, finish off the focaccias (according to taste) with flakes of pecorino cheese and basil leaves.

(1) To prepare sourdough starter at home, take a look here.