Heat oven to 350 degrees Fahrenheit. Grease a 9 by 5- inch loaf pan; set aside. In large bowl, beat eggs with milk and salt until well mixed. Stir in bread crumbs, let stand for 5 minutes to soften.
Add turkey, onion, parsley and thyme to egg mixture; stir until well mixed. Transfer mixture to greased loaf pan. Bake 1 1/4 hours to 1 1/2 hours or until juices run clear when pierced in center of loaf.
Meanwhile, prepare potato frosting: in 2 quart saucepan, heat yellow potatoes with enough water to cover to boiling over high heat. Reduce heat to simmer; cover and cook potatoes until tender-about 12 minutes.
Meanwhile, microwave sweet potato on high until fork tender-6 to 8 minutes. Cut sweet potato lengthwise and scoop pulp into small bowl, avoiding fibrous layer next to skin; set aside to cool slightly. Drain cooked yellow potatoes and return to pan. With potato masher, mash potatoes until smooth. Add milk, 1/2 tablespoon salt, 1 tablespoon butter; mash until creamy. Separate egg, stirring egg white into mashed potatoes. Add egg white into mashed potatoes. Add egg yolk, remaining 1 tablespoon butter, and 1/4 teaspoon salt to sweet potato; mash until smooth and spoon into small pastry bag fitted with 1/4 inch wide star tip. Spoon some of mashed yellow potatoes into large pastry bag fitted with 1/4 inch wide star tip. Set both pastry bags aside.
When meat loaf is done, cool 10 minutes. Carefully strain liquid from meat loaf into 2 quart saucepan and reserve to make gravy, if desired. Unmold meat loaf onto a pizza pan or oven safe serving platter.
Heat oven to 450 degrees Fahrenheit. Pipe sweet-potato mixture lengthwise on top of loaf and around base. Pipe yellow potato mixture all over to cover meat loaf. Bake frosted loaf 15 minutes or until potato browns slightly.
Meanwhile, prepare gravy, if desired. If loaf is baked on pizza pan, with 2 broad spatulas, carefully transfer to serving platter. Garnish with thyme sprigs, if desired. Use serrated knife and sawing motion to slice meatloaf.
In saucepan with reserved meat-loaf liquid, whisk in 1 (14 1/2 ounce) can reduced sodium, nonfat chicken broth, 1 teaspoon Worcestershire sauce, and 1/4 teaspoon ground black pepper. Cook over medium heat, stirring constantly, until thickened and bubbly-about 5 minutes. Yield about 2 cups.
Recipes adapted from Lucy's Garden