Prepare the oven: Preheat oven to 350°F (175°C). Line a large baking sheet with parchment paper. Mix the dry ingredients: Whisk flour, baking powder, nutmeg, cinnamon, and salt together in a medium bowl. 2 ¾ cups 330 g all-purpose flour, 1 ½ teaspoons baking powder, ½ teaspoons nutmeg, ½ teaspoon ground cinnamon, ½ teaspoon fine sea salt
Combine the wet ingredients: In a large bowl, whisk melted butter, granulated sugar, and brown sugar until smooth. Add pumpkin puree, egg, egg yolk, and vanilla. Whisk until well combined.
5 tablespoons 70 g unsalted butter, melted and slightly cooled, ¼ cup 50 g granulated sugar, ¼ cup 50 g packed light brown sugar, ½ cup 120 g pure pumpkin puree, 1 large egg, 1 large egg yolk, 2 teaspoons pure vanilla extract
Make the dough: Add the dry ingredients to the wet mixture. Fold with a spatula until almost combined, then fold in the chocolate chips. Do not overmix. ¾ cup 130 g mini semi-sweet chocolate chips
Chill: Cover and refrigerate the dough for 20 minutes. This makes the sticky pumpkin dough easier to shape.
Shape the logs: Divide the dough in half. Place both portions on the prepared baking sheet, leaving several inches between them. With lightly oiled hands, shape each portion into a log approximately 8 inches long, 3 inches wide, and ¾ inch tall.
First bake: Bake for 28–32 minutes, rotating the baking sheet halfway through. The logs should look set and dry on top with firm edges. A skewer inserted into the center should come out with a few moist crumbs but no wet batter.
Cool: Remove from the oven and let the logs cool on the baking sheet for about 20 minutes.
Slice: Using a sharp serrated knife, gently saw each log into approximately 12 slices, about ⅔ inch thick.
Second bake: Reduce the oven temperature to 300°F (150°C). Arrange the slices cut-side down on the baking sheet. Bake for 15 minutes.
Turn and continue baking: Turn the biscotti over and bake for another 13–17 minutes, until dry and lightly browned around the edges.
Cool completely: For extra-crisp biscotti, turn off the oven, leave the door slightly open, and let them sit inside for about 10 minutes. Transfer to a wire rack and cool completely before serving or storing.