Roasting grapes concentrates their flavor and tightens their texture; when baked on top of focaccia and garnished with rosemary, the result is a flatbread that's excellent for snacking or pairing with cheeses and Italian salumi.
To make the dough: Weigh your flour; or measure it by gently spooning it into a cup, then sweeping off any excess. Combine all of the dough ingredients in a large mixing bowl and mix until a soft dough forms. Knead using a mixer at medium speed for 6 minutes or by hand on a lightly floured surface for 8 minutes, until the dough is smooth and supple.
Transfer the dough to a greased bowl, cover, and let rise for 1 to 2 hours, until doubled.
Wash and drain the grapes.
To assemble: Lightly oil an 18" x 13" baking sheet. Transfer the dough to the pan and gently press it out to fill the pan. If the dough starts to snap back, cover and let it rest for 10 minutes before pressing it out further.
Drizzle 2 tablespoons olive oil over the dough and arrange the grapes across its surface.
Cover the dough with greased plastic wrap or your favorite reusable cover and let it rise for 30 minutes. Remove the cover and gently press the grapes down into the dough; they should be embedded, not resting on top. Re-cover and let rise for another 30 minutes, while you preheat the oven to 375°F.
Uncover the focaccia, add rosemary sprigs and bake for 23 to 27 minutes, until golden brown. Remove from the oven and serve warm.
Store any leftovers, well wrapped, at room temperature for a couple of days; freeze for longer storage.
