Beat the first 5 ingredients at medium speed of a mixer until well-blended. Beat in egg whites. Lightly spoon the flour into dry measuring cups, and level with a knife. Combine the flour, baking powder, and salt; gradually add flour mixture to sugar mixture, beating until blended. Stir in almonds.
Turn biscotti dough out onto a baking sheet coated with cooking spray; with lightly floured hands, shape the dough into a 10-inch-long roll; flatten the roll to a 1-inch thickness. Bake the roll at 325° for 30 minutes. Remove the roll from the baking sheet, and cool for 10 minutes on a wire rack.
Cut roll diagonally into 14 (1/2-inch) slices using a serrated knife. Place the slices, upright, on baking sheet. Bake the slices at 325° for 15 minutes (the cookies will be slightly soft in center but will harden as they cool).
Remove from baking sheet; cool completely on wire rack.
Note: Store in an airtight container. To freeze up to 6 months, place biscotti in an airtight container.