Beat butter in large mixing bowl until light and fluffy. Add sugar and beat until creamy. Beat in egg. Mix in vanilla and orange peel, scraping sides of bowl. In small bowl stir together flour, baking powder and salt. Stir into butter mixture. Do not over-beat or cookies will be tough. Stir in walnuts and chocolate chips by hand. Dough will be firm. Shape dough into 12x2x1-inch log. Using spatula, place log on greased and floured baking sheet. Bake at 325° until light brown, about 30 minutes. Remove from oven and reduce oven. temperature to 300°. Using a spatula, carefully remove log to a wire rack and cool 5 minutes. Return log to cutting board and cut into 12 (1-inch wide) slices, cutting each slice on diagonal. Place each slice on side on baking sheet. Toast biscotti 20 minutes, then flip over and bake until golden brown on both sides and biscotti is hard in texture, another 20 minutes. Biscotti can be frozen or stored in airtight container at room temperature. If frozen, thaw and warm at 325° 5 to 10 minutes to re-crisp. Makes 12 biscotti. NOTE: To toast walnuts, place on baking sheet and toast at 325° 8 to 10 minutes. Remove from oven and then from baking sheet immediately so nuts dont continue to brown. cook 55b