Preheat oven to 275 degrees. Grease a large, heavy cookie sheet.
Mix flour, sugar and baking powder in a large mixing bowl. In another large bowl mix eggs and egg yolks together. Add vanilla, almond flavoring and 1 ¼ cup of the nuts and the zest to the eggs.
Gradually add the dry mixture to the wet mixture, stirring until just barely blended. You will have to use your hands and perhaps add another egg or you can use some of the reserved egg whites if the mixture is too sticky to form.
Using greased hands, form dough into three 4-inch by 9-inch (or thereabouts) rolls that are 2 inches thick. Mixture will be sticky and you will have to use your hands. Using a greased spatula, gently place the “rolls” on greased cookie sheet, making sure the rolls are several inches apart.
Press reserved almonds on top of the shaped dough.
Bake 20 to 25 minutes or until the dough will hold together. Remove from oven and cool slightly. (You must not cool the biscotti too much because they will get too hard to cut). When cooled slightly, gently slide the rolls to a floured cutting board and gently cut through each roll at an angle into 1½- inch pieces. Turn each piece on its side and place on the cookie sheet.
Bake again for 10 to 15 minutes. Remove from oven and turn each piece onto another side. If you prefer harder biscotti, turn biscotti and bake for 5-10 more minutes.