Chopped hazelnuts toast nicely on top of the bread as it bakes. Hazelnut oil drizzled over the cooked focaccia boosts the flavor.
Combine 1/2 cup water, sugar, and yeast in a large bowl, stirring with a whisk; let stand 10 minutes. Add remaining 3/4 cup water and 1 tablespoon hazelnut oil, stirring with a whisk. Lightly spoon flour into dry measuring cups; level with a knife. Add 1 cup flour, 1 teaspoon salt, and ground nutmeg, stirring to combine. Stir in 2 1/2 cups flour. Turn dough out onto a lightly floured surface. Knead until smooth and elastic (about 8 minutes); add enough of remaining flour, 1 tablespoon at a time, to prevent the dough from sticking to hands (dough will feel tacky). Arrange raisins over dough, and gently knead 4 to 5 times or just until the raisins are incorporated into dough.
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in size. (Gently press two fingers into dough. If indentation remains, the dough has risen enough.) Turn dough out into a 13 x 9-inch baking dish coated with cooking spray; gently stretch dough to edges of dish. Cover and let rise in a warm place (85°), free from drafts, for 30 minutes or until doubled in size.
Preheat oven to 400°.
Uncover dough. Make indentations in top of dough using the handle of a wooden spoon or your fingertips. Combine 1 teaspoon water and egg white; brush lightly over dough. Sprinkle with nuts. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in size.
Uncover dough, and drizzle with 2 teaspoons hazelnut oil. Sprinkle dough with remaining 1/2 teaspoon salt. Bake at 400° for 24 minutes or until golden. Drizzle bread with the remaining 1 teaspoon hazelnut oil; let cool slightly.