Preheat oven to 400F.
Drizzle squash with a little EVOO and season with salt, pepper and a little freshly grated nutmeg. Roast cut-side down until tender, about 40 minutes. Let cool enough to handle, then scoop flesh out of skin and add to food processor. Puree squash with stock and honey, in 2 batches if necessary, and reserve.
Heat a drizzle of EVOO in a nonstick skillet over medium-high heat and brown the sausage, crumbling it into very small bits as it cooks, about 7-8 minutes.
While the sausage cooks, heat a pot over medium heat. Add butter and melt, whisk in flour, cook 1 minute then whisk in milk. Season with salt, pepper, a little freshly grated nutmeg and sage. Cook until thickened, about 7-8 minutes, whisking occasionally.
Dot some pumpkin puree in the bottom of a casserole dish then add a layer of pasta. Top with 1/3 of the cooked sausage and cover lightly with pumpkin puree. Cover with another layer of pasta, 1/3 of the bchamel sauce and 1/2 cup Parmigiano. Repeat with 2 more layers, ending each with bchamel sauce and using all of the remaining cheese for the top layer. Sprinkle parsley across the top, cover and bake lasagna 30 minutes. Uncover and cook 15 minutes more to brown the top.
Serve with a spinach salad alongside.