Cinnamon Sugar Biscotti

Ingredients: 
2 cups all-purpose flour
1 ½ teaspoons ground cinnamon
1 teaspoon baking powder
¼ teaspoon salt
1 cup granulated sugar
6 tablespoons (3/4 stick) unsalted butter, room temperature
1 large egg
1 egg yolk
1 teaspoon vanilla extract
Topping:
¼ cup granulated sugar
1 teaspoon ground cinnamon
1 large egg, beaten (for brushing)
Directions: 
1. Preheat oven to 325F. Line two baking sheets with parchment paper or silicone baking mats; set aside.
2. In a medium bowl, whisk together flour, cinnamon, baking powder, and salt; set aside.
3. In the bowl of an electric mixer, cream butter and sugar on medium speed until light and fluffy, about 4 minutes. Add whole egg, followed by egg yolk, beating until combined, scraping down the sides of the bowl as needed. Add vanilla extract. Add flour mixture, beating until ingredients come together to form a slightly stiff dough (holds together when pressed between your fingers and isn’t too sticky).
4. Divide dough between the two baking sheets. Shape each half of dough into a log that measures 9-inches long and 1 ½ inches wide. Press dough down to flatten slightly.
5. In a small bowl mix together cinnamon and sugar for topping. Brush each dough log with the beaten egg and sprinkle generously with cinnamon sugar. Bake for 40 to 45 minutes, rotating halfway through, until biscotto is golden and firm to the touch.
6. Remove from oven, but keep oven on. Let baking sheets cool on wire racks until biscotti is cool enough to handle. With a serrated knife, cut logs into ½-inch wide diagonal slices. Place biscotti cut side down on baking sheets and sprinkle with more cinnamon sugar. Place back in oven and bake again until pale golden, about 10 to 15 minutes.