Preheat oven to 275 degrees. Grease 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 1/4 cups of the nuts, reserving 1/4 cup nuts. Gradually add the dry ingredients to the wet mixture, stirring until just barely blended.
Using greased hands, form dough into three 4-inch by 9-inch rolls that are 2 inches thick. Place 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. 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, cut through each roll at an angle into 1 1/2-inch pieces. Turn each piece on its side and place on cookie sheet.
Bake again for 10 to 15 minutes. Remove from oven and turn each piece onto another side. Bake for 10 more minutes. If you prefer softer biscotti, omit the last 10 minutes of baking.
The biscotti will keep for several weeks if stored in an airtight container. Serve with coffee or tea.