Orange-Pistachio Biscotti

Preheat oven to 300°. Line a large baking sheet with parchment paper or a silicone baking mat.

Place 3/4 cup pistachios, 6 tablespoons granulated sugar and the salt in a food processor. Pulse several times to a sandy grit. Add flour and baking powder. Pulse to combine.

Using a stand mixer fitted with the paddle attachment, beat butter and the remaining 6 tablespoons granulated sugar at medium-high speed until fluffy. Add 2 whole eggs, one at a time, beating after each addition until fluffy. Beat in vanilla and orange zest. Add pistachio mixture; mix on low speed until a soft, slightly sticky dough forms. Mix in the remaining 1 cup pistachios.

Transfer dough to a lightly floured surface. With lightly floured hands, divide dough in half and shape into two logs, each about 6 inches long and 2 inches in diameter. Whisk together egg yolk and the warm water; brush over dough logs. Sprinkle sanding sugar on the work surface. Roll each log in sanding sugar to lightly coat. Set logs on the prepared baking sheet. Pat down logs to about 1 inch high.

Bake just until set, 25 to 30 minutes. Let cool on pan 10 minutes. With a serrated knife, slice each log crosswise into 1-inch-wide cookies. Tip cookies onto cut sides and separate by at least 1/2 inch. Return to oven and bake until golden and dry (they will still be soft in center), 20 to 25 minutes. Let cool on pan 5 minutes. Transfer cookies to a wire rack and cool completely. If desired, dip cookies in or drizzle with melted chocolate.