1. Preheat oven to 350°.
2. Weigh or lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 6 ingredients (through salt) in a medium bowl, stirring with a whisk. Combine vanilla, eggs, and egg white in a large bowl, stirring with a whisk. Add flour mixture to egg mixture; stir until well blended. Divide dough in half. Turn dough out onto a baking sheet coated with cooking spray. With floured hands, shape each dough half into a 12-inch-long roll; pat to 1/2-inch thickness.
3. Bake at 350° for 22 minutes. Remove rolls from baking sheet; cool 10 minutes on a wire rack. Cut each roll diagonally into 18 (1/2-inch) slices. Carefully stand slices upright on baking sheet. Bake biscotti an additional 15 minutes or until almost firm (biscotti will be slightly soft in center but will harden as they cool). Remove biscotti from baking sheet; cool completely on wire rack.
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