3 cups plus 2 tablespoons all-purpose flour
Preheat the oven to 325 degrees. Line 2 large baking sheets with parchment paper (or use nonstick baking sheets). In a large bowl, sift together the flour, cocoa, baking powder, and salt. In a large bowl of an electric mixer, beat the butter and 1 1/4 cups sugar until light and fluffy. Beat in the eggs, one at a time, then add the lemon zest and liqueur. At low speed, add the flour mixture just until combined. Stir in the chocolate chunks and almonds.
Sprinkle a work surface with the remaining 1/2 cup sugar. Divide the dough in half. Roll each piece in the sugar into a 15-inch log. Arrange the logs, 3 inches apart, on 1 prepared baking sheet. Bake for 30 minutes or until center of each log is firm when gently pressed with a fingertip. Cool logs on the baking sheet 1 hour or overnight.
Preheat the oven to 300 degrees. Transfer the logs to a large cutting board. With a serrated knife, slice each log crosswise into 1/4-inch thick slices. Transfer the slices, cut-side down, to the baking sheets. Bake 12 to 15 minutes until crisp. Transfer the biscotti to wire racks and cool completely.
Metropolitan Bakery Cookbook by James Barrett and Wendy Smith Born