1. Preheat oven to 350 °F (175 °C) and line a baking sheet with parchment paper.

2. In a large bowl whisk together flour, baking powder, and salt.

3. Cut cold cubed butter into the dry ingredients until mixture resembles coarse crumbs.

4. In a separate bowl beat eggs, sugar, and vanilla extract until combined.

5. Pour wet ingredients into dry ingredients and stir until just combined.

6. Fold in dried cranberries, white chocolate chunks, and orange zest if using.

7. Divide dough and shape into two 10-inch long logs, about 2 inches wide, on the prepared baking sheet.

8. Bake for 25 to 30 minutes until firm and pale golden, then cool logs for 10 minutes.

9. Slice logs diagonally into 3/4-inch pieces using a serrated knife and place cut side down on the baking sheet.

10. Reduce oven to 325 °F (160 °C) and bake slices for 12 to 15 minutes per side until golden and crisp.

11. Transfer biscotti to a wire rack to cool completely before serving or storing.