For the pork ragu: (This can TOTALLY be done ahead!) Place the garlic, celery, onions and fennel in a food processor and puree to a coarse paste.
Coat a large, wide pot with olive oil and toss in the pureed veg. Bring the pan to a medium-high heat and season generously with salt and a sprinkey dink of crushed red pepper. Cook the veg until they start to get brown and form a crust on the bottom of the pan; be patient...this will take a little time. Scrape the crud off the bottom of the pan and let it re-form. Stay with it and DO NOT let it burn.
Add the ground pork, sprinkle with salt and repeat this process. This takes patience...accept it and move on. THIS is where BIG flavors are formed.
When the meat is nice and brown, add in the tomato paste, stir to combine and cook, stirring frequently, for 3 to 4 minutes. Stir in the white wine and let it cook for 2 to 3 minutes.
Toss in the pureed tomatoes, bay, cinnamon stick, thyme and 2 cups water. Taste and season with salt if needed. Bring to a boil and reduce to a simmer. Simmer until the liquid has reduced by half, add more water and reduce again. Taste and adjust the seasonings if needed. Turn off the heat and use immediately or store for future use.
For the lasagna: Preheat the oven to 350 degrees F. Working in batches, toss the butternut squash slices with olive oil and salt. Lay the squash slices on sheet trays and bake until the squash is tender but still holds its shape, about 20 minutes. Repeat until all the squash is roasted.
Coat a large saute pan with olive oil, toss in 2 of the garlic cloves and a pinch of crushed red pepper and bring the pan to a medium-high heat. When the garlic is golden and very aromatic, remove it and toss it in the "thank you for coming bowl". Add half of the mushrooms to the pan, season with salt and cook until they are soft and wilted. Remove from the pan and reserve. Repeat this whole process--starting with the oil and garlic--with the remaining mushrooms, followed by the spinach in 2 batches. Drain and cool the cooked spinach in a colander or mesh strainer.
In a large bowl combine the ricotta and parsley.
To assemble: Preheat the oven to 375 degrees F. Place a ladleful of the pork ragu in the bottom of a 9-by-13-inch baking dish and spread it around to LIGHTLY cover the bottom of the dish.
Arrange an even layer of the roasted squash on top of the ragu; be sure the squash completely covers the surface of the baking dish--this acts as the "pasta". Cover the squash layer generously with more ragu. Spoon 1-tablespoon scoops of the ricotta mixture over the ragu. Arrange an even layer of spinach and mushrooms over the ricotta. Sprinkle with the grated Parmesan. Lay another layer of squash over the Parmesan and repeat the process until the baking dish is full, ending with a top layer of squash topped with a little ragu and Parmesan.
Cover the baking dish with foil, place on a sheet tray and bake for 45 minutes. Remove the foil and bake for 10 minutes more. Remove from the oven and let rest for 15 to 20 minutes before serving.