at medium speed, scraping bowl often, for 2 to 3 minutes, or until thick and pale yellow in colour.
Add oil, orange juice, orange peel and vanilla; beat 1 to 2 minutes, or until well mixed. Combine flour, walnuts, baking powder and salt; gradually add to egg mixture. Mix on low speed for 1 to 2 minutes, or until well mixed. Stir in cherries by hand.
Turn dough onto lightly floured surface (dough will be soft and sticky). LIghtly sprinkle with additional flour; knead flour into dough. With floured hands, shape into 2 logs. Place 3 to 4 inches apart on a greased baking sheet; flatten tops slightly. Combine egg white and water; brush on logs. Sprinkle with granulated sugar.
Bake in a preheated 350ºF oven for 25 to 30 minutes, or until light brown or firm to the touch. Let cool on baking sheet for 15 minutes. Reduce oven temperature to 300ºF.
Cut cherry biscotti diagonally into 1/2-inch slices with a serrated knife; arrange slices, cut side down, on baking sheet. Bake 8 to 10 minutes, remove from oven, and turn slices. Bake another 8 to 10 minutes or until golden brown. Place cherry biscotti on wire rack; let cool completely.