1Heat oven to 350°F. Grease bottom only of 8x4-inch loaf pan with shortening or cooking spray.
2In large bowl, mix flour, baking powder, cinnamon and salt. In medium bowl, mix brown sugar, oil, milk, vanilla and eggs. Add egg mixture to flour mixture; stir gently until dry ingredients are moistened. Fold in shredded sweet potato and parsnips. Pour batter into pan.
3Bake 1 hour 10 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; run knife around edges of pan to loosen loaf. Remove from pan to cooling rack; cool completely, about 1 hour.
4In small microwavable bowl, microwave frosting uncovered on High 10 to 20 seconds or until melted. Spoon over loaf. Sprinkle with pecans.