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

2. Whisk flour, baking powder, and salt in a large bowl.

3. Beat melted butter, sugar, eggs, vanilla, and sourdough starter until smooth.

4. Gradually stir dry ingredients into wet until a firm dough forms.

5. Fold in cranberries, white chocolate, and orange zest.

6. Divide dough and shape into two 10×2.5 inch logs on the baking sheet.

7. Rest logs 10–15 minutes, then bake 25–30 minutes until golden and firm.

8. Cool logs on the sheet 10 minutes, then on a wire rack 20–30 minutes.

9. Reduce oven to 325°F. Slice logs diagonally into 3/4 inch pieces with a serrated knife.

10. Arrange slices cut side down and bake 10–12 minutes, flip, then bake 8–10 more minutes until dry.

11. Cool biscotti completely on a rack.

12. Optional: Drizzle melted white chocolate over cooled biscotti and let set.