Combine first four ingredients in large bowl. Cut in 3 tablespoons butter (or margarine) using two knives until mixture resembles tiny pebbles. In separate bowl, whisk together eggs, additional egg yolks, vanilla extract. Make a well in center of flour mixture. Add egg mixture dough with spoon. Once all liquid has been absorbed, use the warmth of your hands to incorporate into ball. Dough will be very sticky. Remove dough from bowl to lightly floured surface. Knead dough from 2 to 5 minutes until it is smooth and forms a ball. Dough will still be stick so keep flour under it at all times. Divide dough into 2 balls. Roll each ball into log approximately 10 to 12 inches long and 1 1/2 inches wide. Brush off excess flour and bake on lightly greased parchment paper at 350 degrees for 30 minutes. Remove biscotti from oven and let it rest for 5 to 10 minutes. Reduce heat to 300 degrees. Cut the biscotti into 3/4 to 1 inch wide slices with a sharp knife. Lay cut side down on same pan. Bake 7 more minutes at 300 degrees (see note below). Meanwhile, melt 1/2 stick of butter (or margarine). Combine 1/2 cup sugar and 2 teaspoons cinnamon in a small bowl. Remove biscotti from oven. Using a small spoon, drizzle melted butter over length of each biscotti piece. Sprinkle with sugar and cinnamon mixture. Makes approximately 30 pieces. Store in airtight container. Will last 1 to 2 weeks. Note: For crispier biscotti, increase baking time to 12 to 15 minutes during the second bake.