Preheat oven to 300=B0F. Grease and flour baking sheet. Using an electric mixer with a dough hook attachment, combine flour, 1 C. sugar, baking soda and powder, and salt in a large bowl until blended. In a small bowl, whisk 2 eggs, 1 egg yolk, vanilla, and orange zest. Add egg mix to flour mix; continue beating until a soft dough forms. Turn onto a lightly floured surface. Add walnuts and knead 3 minutes or until walnuts are evenly distributed. Divide dough in half. On baking sheet, shape each piece of dough into a 2 1/2 x 10-inch loaf, flouring hands as necessary. Allow 3 inches between loaves on a baking sheet. In a small bowl, combine remaining 2 T. sugar and cinnamon. In another small bowl, beat remaining egg and water. Brush loaves with egg mixture; sprinkle with sugar and cinnamon mix. Bake 45 to 50 minutes or until loaves are lightly browned. Cool 10 minutes on baking sheet. Cut loaves diagonally into 1/2 inch slices. Lay cut cookies flat on a baking sheet. Bake 15 minutes, turn cookies over, and bake 15 minutes longer. Transfer cookies to wire rack to cool completely. Store in an airtight container. Makes about 2 1/2 dozen biscotti. Recipe By : Nancy Dooley ----