Preheat oven 375F. Lightly grease ex-large cookie sheet or line with parchment paper; set aside. In a large mixing bowl beat butter with electric mixer on medium to high speed for 30 seconds; add sugar and baking powder, beat until combined, scraping sides of bowl. Beat in eggs, maple syrup and vanilla until combined. Beat in flour as much as you can with mixer, now using a wooden spoon, stir in remaining flour and 1 cup of chopped toasted pecans. Divide dough in half, if necessary cover and chill for 1 hour or until easy to handle. Shape each log into 9" long loaf. Place 4" apart on prepared cookie sheet, sprinkle with the 1/3 cup finely chopped pecan, press into top of loaves, flatten loaves to 3" wide. Bake in oven for 20 - 30 minutes or until wooden tooth pick comes out clean when inserted in center. Cool loaves on cookie sheet on a wire rack for 15 minutes. Reduce oven temperature to 325F. Transfer loaves to cutting board , with serrated knife cut diagonally 1/2" thick slices. Place cut side down on cookie sheet, bake in oven for 8 minutes, turn slices over, baking 8 - 10 minutes more or until dry and crisp. Drizzle with maple icing. To make Maple icing mix powder sugar and 1 Tbsp at a time of the maple syrup until icing is able to drizzle. Place Biscotti on waxpaper until icing sets. Transfer Biscotti to wire rack to cool completely. Store Biscotti in an airtight container. Makes 24 Biscotti.