How to Make It
Preheat oven to 375°. Cook sausage in 1 Tbsp. olive oil in a large skillet over medium-high heat, stirring often, 4 to 5 minutes or until meat crumbles and is no longer pink. Remove sausage to a plate, using a slotted spoon; reserve drippings in skillet. Reduce heat to medium.
Stir garlic, 1/2 tsp. salt, half of turnip greens, 1/2 cup water, and remaining 1 Tbsp. oil into hot drippings. Cook 1 minute, stirring and scraping bottom of skillet to loosen browned bits. Stir in remaining turnip greens. Reduce heat to medium-low, and cook 5 to 6 minutes or until greens are tender and water has evaporated. Remove from heat.
Microwave milk, in batches, in a microwave-safe measuring cup covered with plastic wrap at HIGH for 2 to 3 minutes or until very warm. Melt butter in a large saucepan over medium heat. Whisk in flour, and cook, whisking constantly, 1 minute. Gradually whisk in warm milk; cook, whisking often, 12 to 14 minutes or until mixture thickens and comes to a low boil. Remove from heat, and whisk in dry mustard, 1 cup Parmesan cheese, 1/4 tsp. pepper, 1/4 tsp. nutmeg, and 1 tsp. salt.
Whisk together pumpkin, 3/4 cup Parmesan cheese, 1/4 tsp. ground nutmeg, 1 tsp. salt, and 1/2 tsp. pepper in a large bowl.
Place 1 layer of lasagna noodles in a lightly greased (with cooking spray) 13- x 9-inch baking dish, covering bottom completely. (Use pieces of noodles to fill in any gaps.) Spread 1 cup sauce over noodles; top with cooked sausage. Add another layer of noodles and 1 cup sauce; top with half of pumpkin mixture. Add another layer of noodles and 1 cup sauce; top with turnip green mixture. Add another layer of noodles and 1 cup sauce; top with remaining pumpkin mixture. Add another layer of noodles and 1 cup sauce; top with remaining 1/4 cup Parmesan cheese.
Bake at 375° for 40 minutes or until top is golden brown. Let stand 15 minutes before serving. Sprinkle with freshly grated Parmesan cheese. Serve with remaining sauce.