How to Make It
Preheat oven to 400°F. Combine butternut squash, mushrooms, pepper, 1/2 teaspoon of
the salt, and 1 tablespoon of the olive oil in a large bowl; toss to coat. Transfer squash
mixture to a rimmed baking sheet. Spread in an even layer, and bake in preheated oven
until tender, about 20 minutes.
Heat remaining 1 tablespoon oil in a skillet over medium-high. Add onion, and cook,
stirring occasionally, until caramelized, 25 to 30 minutes. Transfer to a plate.
Combine milk, garlic, thyme sprigs, and oregano sprig in a medium saucepan over
medium-high; bring to a boil. Remove from heat; cover, and let stand 30 minutes. Use a
slotted spoon to remove herbs from milk; discard herbs.
Add sausage to skillet over medium-high; cook, stirring often, until browned, 8 to 10
minutes. Transfer sausage to a bowl lined with a paper towel.
Melt butter in a medium saucepan over medium-high. Whisk in flour, whisking
constantly, until there are no lumps. Gradually whisk milk into butter mixture; cook, whisking often until mixture thickens, 5 to 7 minutes. Whisk in Parmesan cheese, nutmeg, and remaining 1 teaspoon salt until smooth, about 20 seconds.
Combine squash mixture, onions, sausage, and zucchini noodles in a large bowl. Pour
butter mixture over squash mixture; toss to coat. Transfer to a buttered 9- x 13-inch
baking dish. Sprinkle evenly with mozzarella, and bake in 400°F oven until golden and
bubbly, 30 to 40 minutes. Sprinkle with fresh thyme leaves.