Preheat oven to 275 degrees. Grease a heavy cookie sheet. Whisk together the flour, sugar, baking powder in a medium size mixing bowl. Whisk the eggs and egg yolks in a large mixing bowl. Add flavorings: mouse extract.
Gradually add the dry mixture to the wet mixture, stirring until just barely blended. You will have to use your hands and perhaps a wee bit of the egg yolk. Add more flour if the mixture is too sticky.
Using greased hands, form dough into three 4-inch by 9-inch (or thereabouts) rolls that are 2 inches thick. Gently place the “rolls” on the cookie sheet, making sure they are several inches apart. Place on a cookie sheet.
Bake for 20 to 25 minutes or until dough will hold together. Remove from oven and cool slightly. (Do not cool completely because you won’t be able to cut it.) When cooled slightly, gently slide the rolls to a floured cutting board. Gently cut through each roll at an angle into 1 1/2-inch pieces. Turn each piece on its side and place on the cookie sheet.
Bake again for 10 to 15 minutes. Remove from oven.
If you prefer a harder biscotti turn onto the other side and bake for 10 to 15 minutes more.