In the bowl of an electric mixer, stir together the water, milk, sugar, and yeast. Let it sit until foamy.
Add the flour, salt, and olive oil to the yeast mixture and mix well.
Knead the dough for 8 minutes.
Let the dough rise until doubled in size, about 1 ½ to 2 hours.
Divide the dough, shape it, and let it rise again for 1 ¼ hours.
Preheat the oven to 450°F.
Brush the dough with olive oil, top with grapes, rosemary, sugar, and sea salt.
Bake for 15 minutes, until golden brown.
Let cool before serving. Serve warm or at room temperature.
