In a large bowl or the work bowl of an electric mixer, dissolve the yeast in the milk and add 1 tablespoon sugar and 1 cup of the flour. Mix well and let stand in a warm place about 15 minutes for the yeast to activate.
In a small saucepan, warm 1/4 cup of the olive oil with the rosemary and lemon zest. Add the grapes and raisins, mix well then add 1/2 to the yeast mixture. Mix another 1 cup flour into the yeast mixture with the dough hook attachment. Knead until smooth. With machine running, add the salt and remaining 3 cups flour, 1 cup at a time, kneading until smooth after each addition. Knead another 6 minutes after the addition of the last cup of flour. The dough should remain rather wet to ensure a soft and light bread. Shape the dough into a ball on a floured board and put it in an oiled bowl. Cover with a damp towel and allow to rise in a warm place until doubled in bulk about 45 minutes.
Punch dough down and lightly sprinkle work surface with flour. Turn out dough and knead lightly. At this point, dough may be wrapped and frozen.
To bake, preheat oven to 400 degrees F.
Oil an 11 by 17-inch baking sheet. Press dough down into a flat disk with the heel of your hand. Using your fingertips, nudge the dough into a rectangle. The dough can be rolled but the pressure will produce heavier bread. Transfer the dough to the baking sheet and brush with the remaining olive oil. Let rise again until doubled, 30 to 40 minutes.
Make indentations all over the dough by pressing with your fingertips being careful not to puncture all the way through the dough. Bake 15 minutes then remove from the oven and brush with the egg. Sprinkle with the remaining grape mixture then the remaining sugar. Finish with some coarse salt. Return to the oven and continue to bake until golden brown on top and crisp on the bottom, about 10 minutes. Let cool in the pan before cutting.
(c) NapaStyle Inc., November 2000 by M. Chiarello, rewrite by D. Shalleck Adaptation from Flavored Oils