1. Preheat oven to 350°. Line 2 baking sheets with parchment paper.
2. Beat butter and sugar at medium speed with an electric mixer until fluffy. Beat in eggs and vanilla.
3. Combine flour and next 3 ingredients in a large mixing bowl. Add flour mixture to sugar mixture, beating until blended. Stir in pistachios and cherries.
4. Place half of dough on each prepared baking sheet. Shape each half into a slightly rounded log about 10 x 3 inches using floured hands. (Dough will be very sticky.)
5. Bake 25 to 30 minutes or until dough is firm to the touch. Let cool completely on baking sheet on a wire rack.
6. Transfer logs to a cutting board, and cut into 1/2- to 3/4-inch-wide slices with a serrated knife. Place slices, cut sides down, on a baking sheet. Bake 4 minutes on each side or until crisp. Transfer to wire racks to cool completely.
7. Dip ends of biscotti in dark chocolate, and drizzle with white chocolate, if desired. Place on wax paper to set.