Preheat the oven to 325. Combine the flour, sugar, salt, zest, anise seeds and baking powder in a mixer. Start on low with paddle attachment. In a separate bowl, whisk the eggs, yolks and vanilla. Add the egg mixture to the dry ingredients, combine and then mix in the nuts until the dough just comes together.
On a lightly floured board, roll the dough into 3 equal logs, and place them on a sheet pan with parchment paper. Make sure the logs are rounded, as the dough likes to flatten in the oven. Bake for about 20 minutes. Cool the logs. Lower the oven to 300. Slice the logs evenly at a slight angle. Lay the biscotti flat on the same pan and bake them for another 15 minutes at 300, until lightly golden and dry. Cool and serve with vin santo, coffee or espresso