►Add potatoes to a large saucepan and cover with water. Bring to a boil and cook until tender when pierced, 15 to 20 minutes. Drain and puree in food processor until smooth. You should have about 1½ cups of puree. Set aside.

►Combine ground turkey, onion, and garlic in a Dutch oven set over medium heat and cook until well browned. Add crushed tomatoes and tomato paste. Season with 1 teaspoon salt, ½ teaspoon pepper, thyme, and oregano. Simmer, covered, for about 30 minutes, stirring occasionally. If sauce

appears to be drying out, add up to ½ cup water.

►Once meat sauce is nearing completion, bring a large pot of lightly salted water to a boil. Cook lasagna noodles in boiling water according to package directions. Drain noodles and rinse with cold water.

►Combine ricotta, 1½ cups sweet potato puree, egg, 1 teaspoon salt, and ½ teaspoon pepper in a large bowl.

►Heat oven to 375° F. Grease a 9-inch-by-13-inch baking dish. Spread 1½ cups of meat sauce in the bottom of the baking dish. Arrange 4 noodles, overlapping slightly, lengthwise over the sauce. Cover with ½ cup ricotta mixture and sprinkle with a layer of Gruyère. Spoon 1½ cups meat sauce over cheese, then sprinkle with a layer of parmesan cheese. Repeat layers, switching the direction of the noodles from lengthwise to widthwise with each layer. Top the final layer of noodles with meat sauce and a generous sprinkle of both parmesan and Gruyère. Cover dish tightly with foil coated with cooking spray. Bake for 30 minutes. Uncover and bake for 10 to 15 additional minutes until cheese is browned and bubbly.