Anything Goes Biscotti

Place racks in upper and lower thirds of oven; preheat to 350°. Beat 1 cup (200 g) granulated sugar, 9 Tbsp. unsalted butter, room temperature, 1 Tbsp. vanilla bean paste or vanilla extract, and 1½ tsp. Diamond Crystal or 1 tsp. Morton kosher salt in the bowl of a stand mixer fitted with a paddle attachment on medium-high speed until light and fluffy, about 3 minutes. With the motor running, add 3 large eggs, room temperature, one at a time, beating until incorporated after each addition and scraping down sides as needed, about 3 minutes total.

Turn off mixer and add 3 cups (375 g) all-purpose flour, ⅓ cup (35 g) unsweetened Dutch-process cocoa powder (if using), and 2¼ tsp. baking powder. Mix on low speed just until dough comes together and no dry streaks remain, about 1 minute. Mix in 2 cups mix-ins (such as coarsely chopped dried fruit, nuts, and/or chocolate chips) if desired.

Transfer dough to a generously floured surface and press together. Divide in half and form each into a 10x2" log. (If dough is sticky, coat in flour.) Transfer each log to a parchment-lined baking sheet and flatten slightly with your hands until about 2½" wide and ¾" thick. If using coarse sugar or flaky sea salt, brush loaves with a thin layer of water and sprinkle sugar or salt evenly over. Chill in freezer 10 minutes.

Bake loaves, rotating baking sheets top to bottom and front to back halfway through, until firm and golden, 25–35 minutes. Let cool slightly.

Reduce oven temperature to 325°. Working one at a time, carefully transfer loaves to a cutting board. Using a serrated knife, cut each loaf on a slight diagonal into ¾"-thick slices. Arrange biscotti, cut side down, on baking sheets and bake, rotating pans top to bottom and front to back and turning biscotti over halfway through, until golden brown and crisp, 20–25 minutes. Let cool on baking sheets.

If dipping the biscotti in chocolate, combine 1 cup white, bittersweet, or semisweet chocolate chips and 1 Tbsp. refined coconut oil in a microwave-safe bowl and microwave on high in 30-second bursts, stirring after each burst, until melted and smooth, 1–2 minutes total. Dip half of each biscotti in chocolate mixture, allowing excess to drip back into bowl, and return to baking sheets. Let sit until chocolate mixture is set and firm, 2–4 hours. After biscotti has set about 30 minutes, use any leftover chocolate mixture to drizzle over if desired. (If the excess chocolate has hardened, microwave in 10-second bursts until melted again before using.) Do Ahead: Biscotti can be baked 2 weeks ahead. Store airtight at room temperature, or freeze up to 2 months ahead.