Add the remaining water, milk, sugar, and flour to the starter and knead well. Then add the olive oil, one tablespoon at a time, letting it absorb before adding more. Finally, add the salt. You'll have a smooth dough ball. Place it in a large bowl dusted with a little flour, cover, and let it rise in the turned-off oven for 3 hours.

Prepare the grapes by washing and drying them, and get the rosemary ready. Also, line a pizza pan with parchment paper and divide the dough in half.

Take half the dough and stretch it out with your hands in the pan. It doesn't have to be perfect; it will even out during the next rise. Press half the grapes and some rosemary needles into the dough. Use a little flour to help stretch the other half of the dough on a work surface, then place it on top of the ciaccia. Press in the remaining grapes and use your hands to pinch the edges closed.

Let it rise in the turned-off oven for another 2 to 3 hours, but not less than 1 hour. Finally, drizzle with olive oil, sprinkle with sugar and rosemary. Bake in a preheated oven at 350°F (180°C) for 25–30 minutes. You can enjoy it warm or at room temperature, but let it rest at least 10 minutes before serving. You'll love it!