Bring a large pot of water to a boil over high heat and heat your oven to 425ºF. Grease a 9-inch square baking pan and set aside.
When the water is boiling, season well with salt and cook the pasta for 1 minute less than the package directs. Drain and set aside.
Place the pot back over the heat and turn it down to medium-high. Add in a splash of oil, remove the sausage meat from its casings, and add to the pot. Use a spoon to break the sausage meat up and cook for 5 to 7 minutes, stirring frequently, until golden and cooked through. Stir in the garlic and continue to cook for 1 minute.
Turn the heat down to medium-low and carefully add the crushed tomatoes, cream, Parmigiano Reggiano, dry Italian seasoning, and sugar and season with salt and pepper. Simmer the sauce for 10 minutes to bring the flavours together.
Scoop about 1 cup of the sauce from the pot and set aside in a small bowl to use later. Add the cooked noodles to the pot of sauce along with the spinach and stir well to combine.
Transfer the saucy noodles to the prepared baking pan and spread into an even layer. Spoon the reserved sauce overtop and scatter with the cheese and pepperoni. Bake the casserole for 15 to 20 minutes until golden brown and bubbling.
