Make Cornmeal Pastry: Combine flour, cornmeal, and salt in a medium bowl. Using a pastry blender or 2 knives, cut in butter until mixture resembles coarse crumbs. Whisk together egg, vinegar, and 1 tablespoon ice water in a small bowl. Sprinkle over cornmeal mixture, tossing with a fork just until dough holds together, adding remaining 1 tablespoon water if necessary. Shape dough into 2 balls, one slightly larger than the other. Flatten into thick disks. Wrap well in plastic wrap and refrigerate at least 30 minutes or overnight.

Make Filling: Meanwhile, combine chicken with 1 teaspoon salt and enough water to cover in a large saucepan. Bring to a boil, reduce heat, and gently simmer 10 minutes. Drain, then cool to room temperature. Shred chicken into bite-size pieces.

Meanwhile, squeeze excess liquid from spinach. Heat oil and butter in a large skillet over medium-high heat. Add spinach, garlic, raisins, pine nuts, and prosciutto. Cook, stirring occasionally, until liquid is evaporated, 5 minutes. Transfer to a large bowl. Add chicken, eggs, cream, remaining 1/2 teaspoon salt, and the pepper.

Heat oven to 350 degree F. Roll larger pastry disk between 2 sheets of lightly floured waxed paper to an 11-inch circle. Remove top sheet of waxed paper, invert and fit into a 9-inch pie plate. Remove second sheet of waxed paper. Spoon filling into pie plate. Roll remaining pastry between 2 sheets of lightly floured waxed paper to a 10-inch circle. Remove top sheet of waxed paper and brush edge of bottom pastry with water; place, brushed side down, over filling. Remove second sheet of waxed paper. Press edges to seal; trim and flute edges. Cut vents on top crust. Bake 45 to 50 minutes, until pastry is golden brown. Let stand 10 minutes before serving. Makes 8 servings.