Preheat the oven to 400°
Peel the butternut squash, slice in half, and scoop out the seeds. Cut each half into ½ in slices, then cut each slice into ½ inch match sticks, and then the sticks into ½ in cubes.
Sprinkle the cubed squash with salt, pepper, sage and nutmeg, and drizzle on olive oil. Toss to coat
Spread the squash on a line baking sheet and cook for 30-40 minutes or until tender, tossing halfway
Meanwhile, in a large pot of salted boiling water, cook your pasta according to package directions until al dente
Strain the pasta and place the empty pot back on the stove. To it, add 1 tbsp of butter and a diced onion. Cook the onion for 1-2 minutes or until fragrant, and then add in the Italian sausage.
Cook the sausage until no longer pink, and set the sausage onion mixture aside.
Add the remaining butter to the pan along with the minced garlic and cook for one minute or until fragrant.
Add in the salt, pepper, sage, thyme, oregano, and nutmeg to toast in the butter. When the butter begins to deepen in color, deglaze the pan with the stock.
Add in the heavy cream and bring to a simmer. Mix in the parmesan cheese, whisking to avoid clumps, and continue to simmer for 2-3 minutes to thicken.
Add back in the sausage and onion mixture, the cooked pasta, and the roasted squash.
Add in the fresh spinach and toss to incorporate. At this point you can turn off the heat, the heat from the pasta and sauce will wilt the spinach.
Garnish with additional parmesan and sage leaves, and serve immediately.