Sift the flour, sugar, baking powder and salt into a large mixing bowl. Cut in
the butter and stir the mixture into a crumbly consistency.
In a small bowl, beat the eggs together with the anise extract and lemon zest,
then combine with the flour mixture. Gently stir the mixture for a few moments
until it becomes doughy and is easy to handle. Next, roll the dough into
thumb-sized logs about 2 inches long by 1 inch in diameter or longer, if
desired.
Lightly beat the egg whites with a tablespoon of water. Brush the pieces with
the egg whites, then dredge and gently embed the sesame seeds onto and
thoroughly covering the pieces.
Place the biscotti on the buttered pan and bake in the preheated oven for about
30 minutes, or until the seeds are lightly toasted.