We dialed back the sausage, boosted the veg way up, and swapped in whole-grain noodles for a dish that’s so good, you’ll wonder why you ever made baked pasta any other way.
Cook pasta according to package directions, omitting salt and fat. Drain and place in a large bowl. Preheat oven to 350 degrees F.
Heat 1 tablespoon of the oil in a large skillet over medium-high. Add sausage, and cook, stirring to crumble into small pieces, until well browned, about 6 minutes. Remove sausage with a slotted spoon, and add to pasta. Add mushrooms to drippings in skillet; cook, stirring often, until lightly browned, 6 to 8 minutes. Add kale to skillet, and cook, stirring often, until kale is wilted, 1 to 2 minutes. Add mushrooms and kale to pasta mixture. Heat remaining 1 tablespoon oil in skillet over medium-high. Add squash, and cook, stirring occasionally, until lightly browned, about 5 minutes. Add 2 tablespoons water. Cover and cook, stirring occasionally, until squash is tender, 5 to 7 minutes. Add squash and 1/2 teaspoon of the salt to pasta mixture.
Melt butter in a medium saucepan over medium-high. Whisk in flour, and cook, whisking constantly, 1 minute. Slowly whisk in milk, sage, and remaining 1/4 teaspoon salt. Bring mixture to a boil, whisking constantly, and cook, whisking often, until thickened, about 1 minute. Remove from heat, and whisk in Parmesan. Pour sauce over pasta mixture; add 1/2 cup of the mozzarella, and stir until well-coated. Spoon into a lightly greased (with cooking spray) 13- x 9-inch (3-quart) baking dish. Sprinkle with remaining 1/2 cup mozzarella.
Cover and bake in preheated oven until cheese melts and mixture is hot, about 20 minutes.