Preheat oven to 350 degrees F (175 degrees C). Grease a cookie sheet.
In a medium bowl, stir together flour, sugar, baking powder, baking soda, and salt. Beat in the egg and egg white, then mix in almonds and orange zest. Knead dough by hand until mixture forms a smooth ball.
Roll the dough into a log about 10 inches long; place on the prepared cookie sheet. Press down, or roll with a rolling pin, until log is 6 inches wide.
Bake for 25 minutes in preheated oven. After baking, cool on a rack. With a serrated knife, cut into 1 inch slices. Place slices, cut side down, back onto the baking sheet.
Return them to the oven for an additional 20 to 25 minutes; turning over half way through the baking. Melt the chocolate over a double boiler or in the microwave oven. Allow chocolate to cool but not harden before dipping one side of the biscotti into it. Place cookies on wire racks, chocolate side up, until cool and dry.