In a large mixing bowl or the bowl of an electric stand mixer fitted with a paddle attachment, sift together all but 1 tablespoon of the flour, the sugar, and spices.
Add all but 1 tablespoon of the butter, the 2 eggs, and the egg yolks. Beat or mix with a wooden spoon until well combined and fluffy. Cover the mixing bowl with a damp towel and leave to rest in a cool place for 6 hours.
Use the remaining butter and flour to lightly butter and flour a cookie sheet. Form the dough into rolls with hands.
Place in the oven and bake for 10 minutes.
Remove from the oven and let cool until the logs are just cool enough to safely handle. Using a serrated knife, carefully cut the cookie logs on the bias, into slices that are about 1/2-inch thick.
Let cool to room temperature, each biscotti lying flat on its side, before serving. If you desire harder biscotti, lower the oven to 250 degrees F, lay the resulting slices flat on the cookie sheet and return to the oven for 5 more minutes to dry the biscotti on all sides.
