1. 1. Prepare Your Baking Area: Preheat your oven to 350 F (175 C). Line a large baking sheet with parchment paper.

2. 2. Combine Dry Ingredients: In a large bowl, whisk together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking powder, and salt. Make sure there are no lumps in the cocoa powder; a fine mesh sieve can help if needed.

3. 3. Mix Wet Ingredients: In a separate medium bowl, lightly beat the eggs. Stir in the vanilla extract and the active sourdough starter until well combined. The mixture should look slightly frothy from the starter.

4. 4. Combine Wet and Dry Mixtures: Pour the wet ingredients into the dry ingredients. Mix with a wooden spoon or spatula until just combined. Be careful not to overmix; a few streaks of flour are okay.

5. 5. Fold in Chocolate Chips and Form Loaves: Gently fold in the chocolate chips until they are evenly distributed throughout the dough. The dough will be sticky. Flour your hands lightly and divide the dough in half. On the prepared baking sheet, shape each half into a log, approximately 9-10 inches long and 2 inches wide. They should be relatively flat on top.

6. 6. First Bake (The “Sourdough” Bake): Place the baking sheet in the preheated oven and bake for 25-30 minutes, or until the logs are firm to the touch and slightly cracked on top. Remove from the oven and let them cool on the baking sheet for about 15 minutes. This cooling period is crucial for them to firm up before slicing.

7. 7. Slice the Biscotti: Reduce the oven temperature to 300 F (150 C). Carefully transfer one cooled log to a cutting board. Using a serrated knife, slice the log diagonally into 1/2-inch thick pieces. The slices should be clean and even. Repeat with the second log.

8. 8. Second Bake (The “Crunch” Bake): Arrange the sliced biscotti cut-side down on the same parchment-lined baking sheet. Return to the oven and bake for another 10-15 minutes, flipping them halfway through, until they are golden brown and crisp. The goal here is to dry them out, giving them their characteristic crunch. Let them cool completely on a wire rack. They will crisp up further as they cool.