1. Preheat oven to 350 ° F and line a heavy large baking sheet with parchment paper. I used my Silpat.
2. Combine 2 ½ cups flour, 1 teaspoon baking powder and ½ teaspoon salt in a medium bowl; whisk to blend.
3. Using an electric mixer, beat the sugar, butter, eggs and almond extract in large bowl until well blended. Mix in the flour mixture, then the dried cranberries.
4. Divide the dough in half. Using floured hands, shape each piece into 2 ½-inch-wide, 9 ½-inch-long, 1-inch-high log. Transfer both logs to the prepared baking sheet, spacing them evenly apart. Whisk egg white in small bowl until foamy; brush egg white glaze on top and sides of each log.
5. Bake the logs until they are golden brown (they will spread), about 35 minutes. Place the baking sheet on a rack and let the logs cool completely. Transfer the logs to a cutting board. Using a serrated knife, cut the logs on the diagonal (about 45 degrees) into 1/3-inch-wide slices. Arrange the slices, cut side down back onto the baking sheet. Bake for 10 minutes at 325°F; flip the biscotti over and bake until just beginning to color, about 5 minutes. (Alternatively, you can stand the biscotti up on their bottoms and bake for 15-20 minutes).
6. Transfer the biscotti to racks to cool. At this point, the cookies can be decorated.
7. To decorate the biscotti with white chocolate, break the chocolate into squares or chop it up roughly. Place it in a zip-top freezer bag and set the bag in a microwaveable cup or mug. Melt the chocolate by heating it in the microwave; every 15-30 seconds, stop and squish the chocolate around in the bag. Be sure that there aren’t any lumps left. Snip a very small corner off of the bag and drizzle over biscotti.
8. Let the cookies stand until chocolate sets, about 30 minutes.
9. Pack the cookies into an airtight cookie tin or plastic container.