The cookie so nice they baked it twice! I particularly love biscotti for its long shelf life: Undipped, biscotti will keep up to 2 1/2 weeks in an airtight container (dipped, up to 1 week). They're perfect for when you want to have something homemade on hand for unexpected visitors! —Erin McDowell
Preheat the oven to 350º F. Line two baking sheets with parchment paper.
In a medium bowl, whisk the eggs and sugar until well combined. Add the orange zest and vanilla extract and whisk to combine.
In another medium bowl, whisk the flour, baking powder, and salt to combine. Add this mixture to the eggs, and mix with a rubber spatula until the dough is fully combined. Add the pistachios and mix just to combine. Be careful not to overmix.
Wet your hands with a bit of water or spray them lightly with nonstick spray. Divide the dough in half and shape each into a log on the prepared baking sheets. The logs should be about 2 inches wide.
Bake the logs until they're golden around the edges and they spring back lightly when touched on the surface, 25 to 30 minutes. Cool the logs until they are easily handled, about 30 minutes.
Use a sharp serrated knife to cut the logs crosswise into even pieces about 1/2-inch thick. Place the sliced biscotti back onto the baking sheets, laying flat, and bake again until evenly browned, dry, and crisp, 15 to 20 minutes more. You may want to flip the biscotti over halfway through the second bake to ensure that they bake evenly.
Cool the biscotti completely before dipping them in melted chocolate (if using). Store in an airtight container for up to 1 week (dipped) or up to 2 1/2 (undipped).
I always carry three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's pie. My first cookbook, The Fearless Baker, is out on October 24, 2017.