1. Prepare Your Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking soda, and salt. Make sure there are no lumps and the ingredients are evenly distributed. This ensures consistent flavor throughout your biscotti.

2. Combine Wet Ingredients: In a separate medium bowl, whisk together the unfed sourdough starter, large egg, and vanilla extract until well combined. The mixture should be smooth and slightly frothy.

3. Mix Dough Together: Pour the wet ingredients into the dry ingredients. Stir with a wooden spoon or spatula until just combined. The dough will be thick and shaggy. Be careful not to overmix, as this can lead to tough biscotti.

4. Fold in Cherries and Chocolate: Add the chopped dried cherries and semi-sweet chocolate chips to the dough. Use your hands to gently knead the mixture a few times in the bowl until the cherries and chocolate are evenly distributed.

5. Shape the Logs for First Bake: Lightly flour your hands and a clean work surface. Divide the dough in half. Shape each half into a log, approximately 10-12 inches long and 2 inches wide. Place these logs onto a baking sheet lined with parchment paper, leaving ample space between them as they will spread slightly.

6. First Bake (Loaf Stage): Preheat your oven to 350 F (175 C). Bake the logs for 25-30 minutes, or until they are firm to the touch and lightly golden brown. Remove the baking sheet from the oven and let the logs cool on the sheet for about 10-15 minutes. This cooling period is crucial for them to firm up before slicing.

7. Slice and Second Bake (Crisping Stage): Reduce the oven temperature to 325 F (160 C). Carefully transfer one cooled log to a cutting board. Using a serrated knife, slice the log diagonally into 1/2-inch thick pieces. Arrange the sliced biscotti cut-side down on the same parchment-lined baking sheet. Repeat with the second log.

8. Final Crisp: Bake the sliced biscotti for another 15-20 minutes, flipping them halfway through, until they are golden brown and very crisp. The longer they bake in this stage, the crispier they will be. Let them cool completely on a wire rack. They will continue to crisp up as they cool.